302 to 5.0 EFI Swap Computer Pins - Ford Mustang Forum
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post #1 of 8 (permalink) Old 02-02-2016 Thread Starter
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302 to 5.0 EFI Swap Computer Pins

My questions evolve around putting a 1988-1993 5.0 into an older vehicle without all the stock sensors found on a Mustang. No EGR, No Canister, No VSS, No air pump, No air conditioning. I do have BAP, TPS, Mass Air from 1993 Cobra, ECT, ACT...off the top of my head. In fact, I used the 302 v-belts at the time and the harmonic balancer and yes the appropriate flywheel for balance.

Most importantly I am trying to get rid of some codes or make the computer look past some missing elements that would normally be in the system. I need someone familiar with moving pins and the importance of the various sensors within the EEC-IV computer with the A9L code.

I am getting some idle search at startup and the engine is running a bit rich. Very low gas mileage, 8.11 with 10 BTDC timing, 4.56 gears with 37" tires. Did a GT40 upgrade and using 19# injectors. When I first got the timing light aimed at the truck the timing was 19 BTDC with no ping and 87 gas. I do want to verify TDC on my 1975 Bronco Harmonic Balancer. Other than that I have gone back to 10BTDC. I wasn't sure if the more open heads and intake would need any different timing. As I think about it, probably not. Not sure if higher timing might provide better performance. 19 wasn't causing any pinging, and I have read multiple times that each engine is unique, although I don't know how that could be. Timing is timing. There has to be an optimal position.


I have an A9L EEC-IV computer. My 60 pin connector is a little different in wiring that the TMoss version that I was using. I think the reason is that I am using a 1988 Speed Density harness that was later fitted with a Mass Air Flow system.

I'll include three illustrations below. One is the TMoss version I have, and the other is a pin illustration that shows what I have. In some cases I have no wire where a wire is to be, and in other places I have a different color wire than the TMoss Illustration. I will also include the break out for an 1986 Speed Density 60 pin. I think I have figured that the pin difference is related to what equipment came on the various years.

The difference in my 88 speed density harness is:
- No pins or wires for VSS dif+ (dark green/white)
- No pin for VSS dif- (orange/yellow)
- My Pin 17 is wired yellow/black, but Tmoss shows it should be tan and goes to self test
- My pin 38 is blank, but should be the AM1 white/red Air Manage1 Solenoid
- My pin 32 is blank, but should have been AM2 Light green/blue Air Manage 2 Solenoid
- My pin 30 is Purple/yellow and should be black that tells the manual computer that the Clutch is pushed in

What I moved or changed:
- I moved pin 51 to position 38 (white/red) Supposed to be for thermactor
- I moved pin 11 to position 32 (light green/blue)
- I did jump pin 30 to pin 46 to provide a constant ground so that the truck would assume I am in neutral, or have the clutch pushed in. This was the other common solution when these connections aren't available.

A comment about computer and O2 pairing. I believe that the most important part is that the computer matches the O2 harness. In my case, the 74 Bronco C4 is automatic, but it doesn't matter. As long as the computer matches the O2 sensors you are ok. If you not end up frying computer trace 46 because the automatic transmission setup on the actual mustang had sensors that mine does not. Some people believe that all three have to match. It was just important that I had an 8 pin wire set heading out to the O2 harness. I just had to make sure I was wired like an 88 manual transmission O2 harness would be. The jumper goes across the end two plugs and not diagonal.

My KOER Codes:
94 - Secondary air system inoperative. I know this. Don't have one. Is this affecting fuel ratio or startup searching?
44 - Air management system inoperative. Yup. Correct, but again can I trick the computer or is this causing startup searching or richness?
33 - Cannister or EGR valve not operating properly. I think this is related to the code 31 I used to get with the KOEO test. Now I get that the system exists, but just not offering varying voltage, just a steady signal.

My KOEO codes:
81, 82, 85, 84, and 95.

What I have done to chase problems since a melted O2 connector:
- Replaced the IAC for Mustang due to idle surge. Mistake to buy a part to chase a problem.
- Cleaned the Mass Air sensor with appropriate cleaner.
- Rewired the O2 sensor properly. The jumper was in the wrong place
- Bought a Digital Volt Meter and LCD code reader!
- Checked some wire continuity on grounds chasing TPS and MAP voltage. Problem was in the computer. Pin 46. This was a result of the melting of the 8 pin O2 connector on the heads. Voltage was fine before this.
- Opened up the computer and found that two capacitors were leading and not attached to the mother board. Fixed.
- As a result of the short I lost the pin 46 track on the mother board and soldered in a new wire. Continuity checked and TPS and MAP voltage was back on target.
- Each connection I took apart I cleaned with a small file and filled with dielectric grease.
- Found a pin in one connector that was not making a connection and replaced the connector.
- Replaced the MAP sensor with a BP sensor. The harness was 1988 Speed Density and code was telling me it was out of range. Put in BP for 1990 mustang and code cleared.
- I moved pin 51 to position 38 (white/red) Supposed to be for thermactor
- I moved pin 11 to position 32 (light green/blue)
- I did jump pin 30 to pin 46 to provide a constant ground so that the truck would assume I am in neutral, or have the clutch pushed in. This was the other common solution when these connections aren't available.
- Used an EGR replacement plug to clear EGR code. (lots of discussion on this subject as to whether it was better to have no EGR so the computer ignores, or to use a plug. I chose the plug.)
- I re-wrapped the TFI module wires with aluminum foil from the fire wall forward and put coil back over it.
- I had a 40 error with KOER telling me that cylinder 4 had a problem. I checked the injector wire, cleaned the terminals, put in new grease, cleaned the connections on the plug wire, and popped the distributor cap and cleaned the contacts and the rotor. The code appears to have been cleared up.

Logic?:
To think this out, my motor searches for idle for the first 10 to 15 seconds whether hot or cold. If I turn off the engine and then turn it right back on, I still get the same search. So? Is the engine looking for some feedback from something it isn't receiving? And once recognized it just ignores the lack of signal. This has to be related to something other than engine temperature due to the fact that it happens hot or cold.

The wandering idle timing mark just seems to indicate an inconsistent electrical signal of some sort. Honestly the truck idles really well with the exception of running rich. If the engine is running rich, what is happening? What sensor is telling the car to increase fuel flow or cutting back air? Or is a sensor adjusting the timing causing the rich fuel? Is the spark not hot enough? I ran a Motorcraft non-platinum plug gapped at .053 as I recall. If the timing is putting gas in the cylinder too late, then the cylinder isn't having time to burn up all the fuel. What is telling my truck to run rich? And can i disable or fool it?

Hopefully I have given enough background information. My focus is on proper wiring at the ECU to bypass unused sensors and to get rid of idle surge at startup and rich fuel. 8.11 mpg just seems too low!

EGR - I know there is controversy about whether to leave the EGR open and cause the computer to just ignore it as inoperative, or to use a plug that tells the computer that the EGR is there with a base signal, but does not adjust to conditions. I chose the plug.

Computer - I read a lot about this, and same controversy. In the end, and in my case with no electrical connections to the computer, the transmission is irrelevant. The computer is manual and so is the O2 harness setup. If I use the Automatic O2 jumping, then I will burn 46 as the automatic and manual systems communicate differently through the computer.

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post #2 of 8 (permalink) Old 02-03-2016
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33, 81, 82, 84, 85, 44 & 94 are whats called “Soft-Codes”.They dont affect fuel or spark programming. Soft-Codes harmlessly stay dormant in the computer.They're only purpose is to help you repair those systems back to original factory specs.They wont cause the cel to come on either.

When the egr valve is non-operational,the ecm deletes its function in the logic.Theres a good reason why you want the ecm to delete its function.Fuel & timing.When the egr valve is still working,the ecm advances timing & leans the fuel mixture when the valve is open.When the ecm deletes its function,fuel & timing will go back to normal values.The purpose for the plug you purchased=it simply keeps the cel from coming on.Your 88 doesn't have a working cel(unless its a CA car)

When you got ready to rotate the distributer to set timing,did you remove the spout plug before rotating the distributer??
*I'f yes* You're good to go
If you didn't remove it,that's most likely why youre seeing the balancer mark wander.The ecm would have been controlling the timing with the spout still in place & that could cause timing fluctuations vs a steady reading that occurs,when the spout is removed.
*If no* You need to connect the timing light again,pull the spout plug then adjust the distributer.The ecm will advance timing 10-14°+ once you plug the spout back in.It helps if you draw a line across the balancer at the 10° & 14° mark,using Witeout.Timing affects idle too.
Another thing you need to do is the salt & pepper shakers maintenance. A loose or corroded pin at these connecters will cause idle problems, weird driveability issues & false trouble codes.This link will help.
Salt & Pepper (10-pin) Connectors Fix

Test the IAC valve & its wiring.With the sensor disconnected,touch the leads of a multimeter across the IAC pins.You should get 6-13ohms.Now reverse the leads across the pins and you should get very high ohms reading or OL.Now touch one lead to the IAC body & touch the other lead to one of the pins.Do the same test on the opposite pin.You should get a very high ohms reading.
Now turn the key on engine off,touch the (-)lead to ground & touch the (+)lead to the red wire terminal of the IAC valve.You should get 12 volts or battery voltage.
If the tests pass,move on to the base idle reset.The base idle reset instruction link is posted below.If you let the engine idle,disconnect the IAC valve & the engine doesn't stall,that's the sign for a bad IAC valve or the throttle set screw is adjusted too high,making the IAC valve operate above the normal 5-6% duty cycle.You'll be adjusting the TPS too,which is listed in the link.
Summarized/Corrected Base Idle Reset Procedure

A vacuum leak or a broken/disconnected HEGO ground wire can also the engine to run rich.Locate the orange wire (might/might not have a ring terminal on the end of it) near the salt & pepper shakers & make sure its attached to a intake bolt or another good engine ground.Its the o2 heater ground.Check for vacuum leaks.A vacuum leak will cause the o2's to read lean then the ecm will falsely richen the fuel trim to compensate for the additional oxygen in the exhaust.
When you replaced the map with a bp sensor,I assume you left its vacuum port open to atmosphere and didn't connect a vacuum hose to it,right?? If yes,that's good.


1991 Mustang lx
D.S.S. 342ci {10.5:1}
TFS 190cc + track heat
Lunati 61011 .549".565"
Pro-M 76mm maf
Jetronic 30lb inj
QA1 Coilovers
17" Weld ProStar XP's
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post #3 of 8 (permalink) Old 02-03-2016 Thread Starter
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33, 81, 82, 84, 85, 44 & 94 are whats called “Soft-Codes”.They dont affect fuel or spark programming. Soft-Codes harmlessly stay dormant in the computer.They're only purpose is to help you repair those systems back to original factory specs.They wont cause the cel to come on either.
I'm not sure the CEL is connected on the Bronco, but I am reading codes from the tester. Since I have never had the CEL light come on when I was having hard codes, I presume the CEL is not connected.

When the egr valve is non-operational,the ecm deletes its function in the logic.Theres a good reason why you want the ecm to delete its function.Fuel & timing.When the egr valve is still working,the ecm advances timing & leans the fuel mixture when the valve is open.When the ecm deletes its function,fuel & timing will go back to normal values.The purpose for the plug you purchased=it simply keeps the cel from coming on.Your 88 doesn't have a working cel(unless its a CA car)
So do you vote plug, or no plug? It clears the code by giving the computer feedback, but the feedback is constant and doesn't give the computer "valuable" information.

When you got ready to rotate the distributer to set timing,did you remove the spout plug before rotating the distributer??
*I'f yes* You're good to go
If you didn't remove it,that's most likely why youre seeing the balancer mark wander.The ecm would have been controlling the timing with the spout still in place & that could cause timing fluctuations vs a steady reading that occurs,when the spout is removed.
*If no* You need to connect the timing light again,pull the spout plug then adjust the distributer.The ecm will advance timing 10-14°+ once you plug the spout back in.It helps if you draw a line across the balancer at the 10° & 14° mark,using Witeout.Timing affects idle too.

Yes I am pulling the SPOUT, but at low idle the mark is all over. Perhaps that is normal. I do have one mark on the balancer, TDC. I need to confirm its accuracy. I have a variable timing light, so I just set the light to the timing I want and then rotate the distributor back to my TDC mark. The idle screw is completely loose at this point. I can't control it any lower.

Another thing you need to do is the salt & pepper shakers maintenance. A loose or corroded pin at these connecters will cause idle problems, weird driveability issues & false trouble codes.This link will help.
Salt & Pepper (10-pin) Connectors Fix

The wiring doesn't look worn on the top side of the salt and pepper. I did take a rat tail file to all the salt and pepper connections and filled with dielectric grease. When I got the cylinder 4 error I cleaned that particular contact again. That error is now gone. I do know that grounds are important.

Test the IAC valve & its wiring.With the sensor disconnected,touch the leads of a multimeter across the IAC pins.You should get 6-13ohms.Now reverse the leads across the pins and you should get very high ohms reading or OL.Now touch one lead to the IAC body & touch the other lead to one of the pins.Do the same test on the opposite pin.You should get a very high ohms reading.
Now turn the key on engine off,touch the (-)lead to ground & touch the (+)lead to the red wire terminal of the IAC valve.You should get 12 volts or battery voltage.
If the tests pass,move on to the base idle reset.The base idle reset instruction link is posted below.If you let the engine idle,disconnect the IAC valve & the engine doesn't stall,that's the sign for a bad IAC valve or the throttle set screw is adjusted too high,making the IAC valve operate above the normal 5-6% duty cycle.You'll be adjusting the TPS too,which is listed in the link.
Summarized/Corrected Base Idle Reset Procedure

The one part that I did replace was the IAC. I also cleaned the terminals and filed and greased the plug. I will test the voltages. I did reset the computer yesterday. I left the negative terminal off with the lights on for about 3 hours. I was hoping I could take the base idle down lower, but it is adjusted as low as possible. The article I read about base idle reset said to disconnect the IAC and the battery. When I reconnected the battery I left the IAC disconnected until the truck warmed up. It would idle on its own without the IAC. Idles at about 700. I then turned off the engine, connected the IAC and started it back up. The truck surged about 20 times on first start with reset computer. My first trip today it surged about 6 times. It seems to learn the problem, but it may do what it did before. Before it would surge about 4 times, hot or cold, and then idle fine. Maybe I'b being picky, but I am trying to get better mileage and less rich gas. I just assume that the rich fuel mixture is related to....something?

A vacuum leak or a broken/disconnected HEGO ground wire can also the engine to run rich.Locate the orange wire (might/might not have a ring terminal on the end of it) near the salt & pepper shakers & make sure its attached to a intake bolt or another good engine ground.Its the o2 heater ground.
I'll look for that ground. There is a bare wire braided ground that goes to the body where the BAP is mounted. Is that the same ground? I'll double check all grounds. I might take the computer ground and run it directly to the battery negative. Right now it grounds to the metal body.

Check for vacuum leaks.A vacuum leak will cause the o2's to read lean then the ecm will falsely richen the fuel trim to compensate for the additional oxygen in the exhaust.
I think the vacuum lines are all good. This is a fresh rebuild. I just put some new t's on one vacuum line. Used to be one could spray starting fluid around the hoses and find a leak when the engine surged. Does that still work? I am also using a different intake than factory. I wonder sometimes if the amount of vacuum is still the same. If I knew what it should be, I could test the lines. The explorer GT40 intake is different than the 5.0.

When you replaced the map with a bp sensor,I assume you left its vacuum port open to atmosphere and didn't connect a vacuum hose to it,right?? If yes,that's good.
I was getting a code that the MAP/BAP was out of range. I knew it was getting proper voltage so I decided to replace it. It was never connected to the vacuum lines, just left open. However since this was a Speed Density harness I figured that perhaps this was the wrong sensor, so I bought a BAP sensor for a 1990 mustang MAF engine instead. The BAP has a little plug on it to prevent connecting it to the vacuum from the engine. The new BAP did clear the code I was getting earlier.

I will chase down the grounds on the O2 and see if I can find any vacuum leaks. The vacuum may be too low in some cases, but I would have to know what vacuum is expected at each place. Right now the vacuum is only connected to the fuel rail that I can recall. I'm sure there are other place....that I can't picture in my mind right now.

And what of all the pins on the computer? The one's I moved don't seem to have affected anything. Tempted to move them back. I'd just like to know if there is a way to clear the codes, or prevent them by pulling the pins for those sensors. This may save the computer from going out to look for a sensor. Right now they are just on the engine with nothing plugged into them, just like the EGR was. Do they make plugs similar the EGR plug for the canister purge?

I don't get any codes for the coolant temp, air temp, or O2 sensors, so I assume they are working properly. One thing I considered was that my TFI might be bad, but my symptoms don't seem to reflect that. I think in a perfect world I am expecting rock solid electronics, like the timing wandering or other DVM readings. My TPS has been dead on .97 or .98. No problems there.

I will pull the plugs and see if I have any fouling or other indications within the first 1,000 miles. Maybe that will give me some clues. Thanks for your input. If you think of anything else, let me know!
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post #4 of 8 (permalink) Old 02-03-2016 Thread Starter
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302 to 5.0 EFI swap in Early Bronco 1975

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Last edited by Early Bronco; 02-03-2016 at 01:06 PM. Reason: Posted twice
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post #5 of 8 (permalink) Old 02-05-2016
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Angry

You can leave the plug for the egr.I was just giving you a brief description of how the system works when its deleted.

The thing thats most important about the salt & pepper procedure is to make sure you open the male pinouts slightly & close the female pinouts slightly so that both pinouts make a tight connection.

The ground strap that's braided is the secondary ground.Its the ground for the interior/exterior lights,gauges & the alternator.
The HEGO ground wire is part of the fuel injector harness.The wire labeled #19 in the following diagram is the HEGO ground, you need to be looking for.
http://www.veryuseful.com/mustang/te...ineHarness.gif
There's is also a very important ground called the EEC ground.The neg battery cable has a smaller gauge wire that bolts to the fender apron then this same wire forks off & has a round connecter attached.This connecter plugs into another matching connecter that's part of the main wiring harness coming from the computer.Your battery cable will look like the one below and you'll see the other part that connects to it mounted to the fender apron in the picture, if you've got this ground.

As far as the IAC valve goes,check your throttle body blade & see if it has a hole drilled in it.If it does,thats gonna prevent you from setting idle to your desired setting. Its like having the throttle blade open all the time.If you close this hole(if present)it will only you more control over idle.650-750 is a good idle setting though.If the engine doesn't stall when the IAC is disconnected, its usually due to a bad IAC or the throttle screw is open too much or the throttle blade has a hole in it.

I believe vacuum should be between 15-20inHg.You can use carb cleaner or a small handheld propane torch with a 1ft piece of hose attached. Keep a fire extinguisher present though.I like to use a wet towel to protect myself while running the hose alongside any suspect areas where a vacuum leak might exist.

The egr & tab/tad solenoids are the only components in which plugs are available for.Like I stated,their main purpose is to prevent the cel from coming on which you don't have to worry about anyways because of the vehicle you're driving.The egr,smog system components & canister purge being deleted won't cause any driveability issues. Youre gonna smell some gas fumes because of not having these components in place like the egr & canister purge valve.

Vacuum hoses should run to the pcv valve,fuel pressure regulator since you've got the canister purge & egr valve deleted & probably no power brakes.
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1991 Mustang lx
D.S.S. 342ci {10.5:1}
TFS 190cc + track heat
Lunati 61011 .549".565"
Pro-M 76mm maf
Jetronic 30lb inj
QA1 Coilovers
17" Weld ProStar XP's
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post #6 of 8 (permalink) Old 02-06-2016
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Quote:
Originally Posted by Early Bronco View Post
To think this out, my motor searches for idle for the first 10 to 15 seconds whether hot or cold. If I turn off the engine and then turn it right back on, I still get the same search. So? Is the engine looking for some feedback from something it isn't receiving? And once recognized it just ignores the lack of signal. This has to be related to something other than engine temperature due to the fact that it happens hot or cold.
I meant to post the following link a few days ago.It explains the strategies that occur for each type of running condition.
(Example=start/crank,cold start/warmup,etc.)
Fuel Injection Technical Library » Strategies

I don't know if you've already ran through the surging idle checklist or not,but if you haven't here's the link that shows which components to check.
Help me create the "Surging Idle Checklist" | Mustang Forums at StangNet

1991 Mustang lx
D.S.S. 342ci {10.5:1}
TFS 190cc + track heat
Lunati 61011 .549".565"
Pro-M 76mm maf
Jetronic 30lb inj
QA1 Coilovers
17" Weld ProStar XP's
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post #7 of 8 (permalink) Old 02-08-2016 Thread Starter
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Thanks a lot for your input. We just hit a cold spell, so I won't be looking at anything for a week or so. I did look up the pdf article that you mentioned and found it online. I'll include everything I can for the sake of others. If the link ever goes away I'll post the article here, without images. I will keep the pdf on my computer if anyone ever needs it. Lots of good help. Thank you so much!! It gives me some things to chase down.

---------------

It is located at:
http://sth2.com/mustang/EFI-harness-...structions.pdf

The article is titled: Conversion of a ’89-’93 MAF 5.0 Mustang EFI Wiring Harness to Standalone Operation in Another Vehicle

Conversion of a ’89-’93 MAF 5.0 Mustang EFI Wiring Harness to Standalone Operation in Another Vehicle
1. I’ll assume that you already have a place to mount your EEC and that you’ve already cut a hole in the firewall for the harness. If you haven’t done this yet, you’ll need to figure out where you want the EEC and where to cut the hole in the firewall.
2. Prior to removing any wires, I recommend you verify that you are removing the correct wire by performing a continuity check from the harness connector to the 60 pin EEC connector.
3. Removing wires from the Ford connectors is very easy. The first thing you need to do is remove the red plastic retainer. A small pick or other pointed tool and some needle nose pliers is usually all it takes to remove the retainer. Once the retainer is removed, you’ll see the metal terminals and each one will be retained by a plastic barb within the connector. Using a tiny screwdriver, carefully pry the plastic barb away from the wire terminal and pull the wire from the connector. The terminals are inserted from the wire end, so just pull on the wire associated with the terminal and it should slide out of the connector.
4. I am using a 1991 harness for reference. Ford changed some of the colors over the years. The colors referred to are what are present in my harness. Your harness may differ slightly. When a wire color is listed, the first color is the main wire color and the second color is the tracer stripe, if there is one. For example, light green/black would be a light green wire with a black tracer stripe. Some colors fade, run, or may appear to be a different color.
5. When making the modifications, it is easiest if you completely unwrap the harness. Small zip ties are helpful for maintaining the harness somewhat orderly while you are working on it. As you unwrap the harness, you can use small sip ties to hold the wires together into the same bundles they were in when they were wrapped up.
6. For splices, I highly recommend that you solder the connections and cover them with heat shrink tubing. EEC sensors use very small differences in voltage for their signals, and a bad connection can lead to a rough running engine. Don’t just twist the wires together and cover them with tape. I also do not recommend crimp connectors. For heat shrink, I suggest using the marine grade heat shrink that has an adhesive lining and is generally a little thicker – it’s the best way to keep moisture out of your connections. You can find it at marine & boating supply stores such as West Marine. Harbor Freight also sells a kit that is loaded with marine heat shrink – it works great and is the most economical.

7. Prepare your harness for installation in the car. These steps will describe what can be removed from the harness and what must stay.
a. Items i. ii. iii. iv. v. vi. vii. viii. ix. x. xi. xii. xiii. xiv. xv. xvi. xvii.
b. Items i. ii. iii. iv. v. vi. vii. viii. ix.
8. If you do not
that you MUST retain:
60 pin EEC connector
Ground (3 different places)
EEC power relay
MAF connector
O2 harness connector
TFI connector
SPOUT connector
Barometric pressure sensor
Diagnostic link connectors (black & gray – gray has a single wire) Ignition coil connector
+12V power connection (should have a fusible link w/ a ring terminal) Fuel injector connectors (8)
Throttle position sensor
Engine coolant temperature sensor
Exhaust gas recirculation valve position sensor Intake air temperature
Idle air bypass valve
which you may remove:
Emissions air dump valve solenoid Emissions air port valve solenoid
EGR vacuum control solenoid
A/C Wide Open Throttle relay
A/C pressure safety switch connector A/C compressor connector
Canister purge solenoid connector Coolant temperature gauge feed
Oil pressure gauge feed
plan on using any of the emissions control equipment, remove the connectors from the harness as follows:
a. Locate the 3 connectors for the 3 emissions control valves (Thermactor air diverter, Thermactor air bypass, and EGR vacuum control). They look like this:
b. All 3 of these connectors have a red wire which is +12V supply that comes from a splice within the harness. Unwrap the harness to locate the splice and clip these 3 red wires.
c. The remaining 3 wires are the control signals from the EEC. At the 60 pin EEC connector, remove the following wires: Pin 32 (light green/black), 33 (dark green), & 38 (white/red).
d. Locate the Canister Purge Solenoid connector: It looks like this:

e. The red wire is a +12V supply that connects to a splice in the harness just like the 3 connectors that were just removed. Unwrap the harness, locate the splice, and clip the wire.
f. The remaining wire is the control signal from the EEC. At the 60 pin EEC connector, remove the wire at pin 31 (gray/yellow).
9. For air conditioning, you have several options. If you do not have any plans of using air conditioning, you can remove the A/C connections from the harness. If you are using air conditioning and don’t want to connect it to the EFI harness, you can remove the A/C connections from the harness. The engine will run fine, but you will be removing what is known as a “feed-forward” signal to the EEC. When the EEC senses the +12V going to the compressor clutch, it anticipates the load on the engine and increases the idle slightly. Without this input, your engine might stall when the compressor engages with the engine at idle. In all reality, the engine probably will stay running, but may stumble for a second at idle when the A/C compressor engages. Above idle, this signal does not matter. The other EEC control function is WOT (Wide Open Throttle) cutoff. If the EEC senses WOT from the throttle position sensor, it will deenergize the A/C WOT relay and cut power to the compressor. This function is solely to cut the parasitic drag from the compressor at WOT so the engine can put maximum power to the transmission. The A/C compressor and engine will work just fine without this function connected. If you want to use these functions with your air conditioning, it’s easy enough to do. The following steps refer to the A/C WOT relay, pressure safety switch, compressor clutch connector, and the gray round 8 pin connector. They look like this (the WOT relay in my harness was messed with at one time – the crimp connectors should not be there):


a. If you have no plans of using air conditioning or don’t wish to use the EEC control functions for A/C, do the following:
i. Remove the light green/purple wire from the round 8 pin connector. This wire runs directly to the pressure safety switch.
ii. Remove the pink/light blue wire at pin 10 of the 60 pin EEC connector & the orange/light blue wire at pin 64 of the 60 pin EEC connector. These wires go to the WOT relay. An additional pink/light blue wire runs between the pressure safety switch and the WOT relay.
iii. Follow the red wire from the WOT to the splice in the harness. Clip this wire from the splice.
iv. Remove the A/C clutch connector from the harness. It has 2 wires – a black/yellow and black/light green. The black/yellow goes to the WOT relay. Follow the black/light green wire to the splice in the harness and clip this wire from the splice.
v. The A/C WOT relay, pressure safety switch, clutch connector, and associated wiring should now be free from the harness.
b. If you are using A/C and want to use the control functions, it’s very easy to do. Do the following:
i. Remove the light green/purple wire from the round 8 pin connector. Disconnect the power wire going to you A/C compressor clutch and connect this wire to the light green/purple wire.
ii. If your system has a pressure safety switch, clip the existing pressure safety switch connector from the EFI harness. Connect the light green/purple wire to one terminal of your pressure switch (it does not matter which terminal). Connect the pair of pink/light blue wires to the other terminal of the pressure switch.
iii. Connect the black/yellow wire in the clutch connector to your compressor clutch power feed. The black/light green wire is not needed if your compressor clutch is grounded through the compressor case. If your compressor clutch is not grounded through the case, you can use the black/light green wire for your ground.
10. Next will be the various gauge and warning light feeds. None of these connections run to the EEC – they are just part of the EEC harness. The 3 feeds are the low oil level sender, engine temperature sender, and oil pressure sender. You will most likely not use the low oil level sender since this was specific to the later Mustangs – the connector is in the oxygen sensor harness. The sending unit was located in the passenger side of the oil pan. You may want to use the engine temperature and oil pressure wires to feed
your gauges. Locate all of the components:
a. If you have no need for the low oil level sender, remove it from the harness. The sending unit connector is in the O2 sensor harness and has a white/pink wire. Remove the wire from both sides of the O2 sensor harness connectors and from the gray round 8 pin connector. The wire should now be free from the harness.
b. If you want to use the wires for the engine temperature and oil pressure sending units, leave them as is. The oil pressure sender wire is white/red and the engine temperature sender wire is red/white. The oil pressure sender wire is longer and should have a braided sleeve over it. Both of these wires run through the white 10 pin connector (engine harness to main EFI harness connector) and terminate in the black round 8 pin connector. Remove the white/red and red/white wires from the black round 8 pin connector. Connect the red/white wire to your temperature gauge and connect the white/red wire to your oil pressure gauge.
c. If you do not wish to use one or both of the wires, remove the wire(s) that are not needed from both side of the white 10 pin connector and from the black round 8 pin connector.

11. Now for the tachometer feed. It’s a dark green/yellow wire that runs from the negative side of the ignition coil to the gray round 8 pin connector. Remove this wire from the gray round 8 pin connector and connect it to your tachometer feed. If you don’t wish to use this wire, you can remove it from the harness. There is also a dark green/yellow wire that runs from the ignition coil to EEC pin 4 via a 22Kohm resistor. This wire must remain in place. You can remove the extra dark green/yellow wire that feeds the tachometer if you wish.
12. The vehicle speed sensor is not needed if you are running an automatic transmission and not adapting the original cruise control for use on your project. I have heard that the engine will run just fine without the VSS if you have a manual transmission. It’s primary function is to let the computer know that the car is moving above a certain speed. If the EEC senses the car moving and the engine is at idle (i.e. transmission in neutral or clutch pushed in), it will raise the idle by several hundred RPM. Once the car comes to a stop, the engine rpm should drop back its usual speed.
a. If you do not need the VSS, remove the dark green/white wire from EEC pin 3 and the orange/yellow wire from EEC pin 6. These wires run to the black round 8 pin connector – remove these wires from this connector.
b. If you want to use the VSS, remove the dark green/white and orange/yellow wires from the black round 8 pin connector and connect the VSS. I don’t think it matters which terminal of the VSS you connect each wire to, but if you are looking into the connector (form the end that connects to the VSS) with the rounded side to the top, the dark green/white goes on the left and the orange/yellow goes on the right.
13. If you want to use a check engine light, obtain a 12V lamp (auto parts stores have these). Connect one side of the lamp to a source that provides +12V with the ignition switch in “RUN”. For the other terminal, remove the pair of tan wires from the green rectangular 8 pin connector (they both go to the same terminal – one goes to the diagnostic connector and the other goes to EEC pin 17) Connect these 2 tan wires to the other side of the lamp. If you don’t want to use a check engine light, you can leave these wires alone. If you have the original fuel pump relay harness, you can use the tan wire in that harness instead of removing the wires from the green connector.
14. Now make sure your O2 sensor harness jumper is set properly for the type of EEC that you are using. The type of transmission doesn’t matter – the type of EEC does. If you are using an automatic transmission EEC, the jumper should connect between to pins next to each other in the same row so that the purple/yellow wire is jumpered to the white/purple wire in the main harness. If you are using a manual transmission EEC, the jumper should connect between pins in different rows so that the purple/yellow wire is jumpered to the light blue/yellow wire in the main harness. You won’t damage an
automatic transmission EEC if this jumper is wrong, but there is a very high likelihood that you will fry the pin 46 circuit board trace inside a manual transmission EEC if you have the jumper set for an automatic transmission. Check the program code on your EEC and set the jumper accordingly. The actual type of transmission installed doesn’t really matter. There have been slight differences in the O2 harness jumpers over the years, so just make sure that the wire is connected correctly in your harness.
15. If you are not using the emissions equipment, you should install an EGR eliminator plug into the EGR valve position connector in the harness. This plug will tell the computer that the EGR valve is closed at all times. If you don’t install the plug, the engine will run fine, but the check engine light will be lit constantly. EGR eliminator plugs are available from Rjminjectiontech.com. As an alternative, if the EGR valve is still installed on your intake manifold, you can just plug the harness connector into the valve – the valve will always stay shut without the vacuum signal connection.
16. The following wires are for your power sources and grounds and must be connected to an appropriate source.

a. Remove the red/light green and the red/light blue wires from the gray round 8 pin connector.
b. The red/light green wire gets connected to a +12V source that is live with the ignition in the “RUN” position.
c. The red/light blue wire gets connected to a +12V source that is live with the ignition in the “START’ position. The “S” terminal on the starter solenoid is a good place to connect this wire.
17. Find the large orange/black wire (possibly yellow for ’92-’93 models) that has a fusible link with a ring terminal. If the fusible link is missing, it would be a good idea to get a replacement (available in the electrical section of an auto parts store). The fusible link acts like a fuse and burns out when there is a short. Connect this wire to a +12V source that is always live. The battery side of the starter solenoid is a good choice. You could also go straight to the positive battery terminal.
18. There are 3 grounds. One is located near the 60 pin connector, one (may be black/light green, black/white, or black) should be near the constant +12V wire (orange/black or yellow), and the other is an orange wire in the engine harness. The ground near the constant +12V wire may have a quick disconnect that looks similar to an inline fuse holder. All 3 of these need to be connected to a good ground.
19. Now for the transmission connections:
a. For automatics, the neutral safety switch that provides an interlock to prevent
starting the car in gear also provides a signal to the EEC using the same switch. If you are using a manual transmission EEC with an automatic, do not connect this switch to the EEC wiring. If you are using an automatic transmission EEC, remove the white/purple wire from the black round 8 pin connector. If you have the original vehicle harness, this wire changes from white/purple to white/pink at the black round 8 pin connector. If you are using a manual transmission EEC and want the starter interlock protection of the neutral safety switch, removal of the jumper from the O2 sensor harness should protect the EEC.
i. Since automatics don’t use a clutch pedal position switch, you can eliminate the light blue/yellow wire that runs between the O2 sensor harness and the black round 8 pin connector. You can also leave the wire in place – it doesn’t matter either way.
b. For manual transmissions, the starter safety interlock was handled by the clutch position switch mounted on the clutch pedal. Some T5 transmission had a neutral sensing switch, but this switch was not used in the starting circuit – it was used along with a second clutch position switch as a feed-forward signal so that the EEC could anticipate engine loading and increase the idle. Most manual transmissions will not have a neutral sensing switch and the car the engine is
being installed in will probably not have a clutch pedal position switch. You can add one if you wish, but it’s not necessary for the EEC. If you want to use a clutch position switch, you need a switch that is closed (completes the circuit) when the clutch pedal is fully depressed. The switch will open once you start to release the clutch pedal. When the EEC sees the loss of this signal, it anticipates that the engine will be loaded. If you don’t connect it, the engine should run just fine, but the idle may be slightly higher (I don’t know for sure). If you want to connect the switch, remove the light blue/yellow wire from the black round 8 pin connector and the black/white wire from the green rectangular 8 pin connector. Connect these wires to your clutch position switch. If you happen to be using an automatic transmission EEC with a manual transmission, don’t connect the clutch pedal switch.
i. Connect the VSS to the transmission. The engine should run fine without it, but idle characteristics might be affected.
20. Fuel pump relay: The relay will have at least 4, possibly 5, terminals. Terminals 1&2 are the triggering coil for the relay. Terminal 5 will not be used. A connection is made between terminals 3&5 when the relay coil is deenergized, and a connection is made between terminals 3&4 when the relay coil is energized. The coil is energized by applying +12V across terminals 1&2. Terminals 1&2 are the small terminals. Terminals 3,4,&5 are the large terminals. When you look into the relay, you should see the terminals numbered. You will connect the wires listed below to the relay pigtail wire that goes to the specified terminal. You will need the following:
-Fuel pump relay (BWD part # R647)
-Fuel pump relay pigtail (BWD part # PT5613)
-Inertia switch (Available at RJMInjectionTech.com) -Inertia switch pigtail (Available at RJMInjectionTech.com)
a. Remove the following wires from the green 8 pin connector: Red & the 2 wires that are tan/light green stripe.
b. Connect the large red wire to terminal #1 & #3. This wire will provide the +12V to trigger the relay coil and also the +12V to run the fuel pump.
c. Connect the two tan w/light green stripe wires to terminal #2.
d. Terminal #4 is the feed to your fuel pump. The inertia switch should be
connected in series between terminal #4 and the fuel pump. This switch will
automatically cut power to the fuel pump in the event of a collision.
e. If you accidentally switch terminals 1&2, it’s no big deal. The relay will work
either way.
f. If you accidentally switch terminals 3&4, it’s no big deal. The fuel pump will still
work.
g. Terminal 5 is not used. You can remove this wire from the pigtail. If you leave
the wire in the pigtail, ensure that it is properly insulated so that it won’t cause a short.
h. You can mount the inertia switch pretty much wherever you want. The only thing that matters is that the switch MUST be mounted vertically with the reset button on the top. If you mount the switch any other way, it may not function correctly. Mount the inertia switch in a place that is not too difficult to reach – you might have to reset it one day! You can test the inertia switch by giving it a knock with a knuckle or tapping it lightly with a hammer.
21. All the wires should be accounted for now. Install your harness & connect all the sensors. If you are using a manual transmission EEC and want to make sure you don’t accidentally fry it in the event your O2 sensor harness jumper is wrong, do the following:
a. Remove the EEC from the 60 pin connector.
b. Connect a voltmeter between pin 46 of the EEC connector and ground.
c. While watching the voltmeter, crank the engine. If you see voltage (around
+12V) when the engine is cranking, your O2 sensor harness jumper is incorrect.
If you don’t see voltage, you are good to go! d. Reconnect the EEC and give it a shot!
Attached Files
File Type: pdf EFI-harness-installation-instructions.pdf (1.04 MB, 519 views)
Early Bronco is offline  
post #8 of 8 (permalink) Old 02-08-2016 Thread Starter
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Joined: Jun 2014
Location: Topeka
Posts: 33
 
I have vacuum assist brakes... I'm not a complete idiot! Well, I was for the first 30 years of ownership! That was one of those things I did and later thought, "I should have done that YEARS ago!" Thanks again.

And Good news on the article you sent me. I found it online, downloaded the pdf, and was allowed to attach it above. Great info. Thanks. I'll see how things go.
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