Ford Mustang Forum banner
Status
Not open for further replies.
1 - 7 of 7 Posts

·
Registered
Joined
·
4 Posts
Discussion Starter · #1 ·
This is a great forum - thanks to all of you who post questions and answers - I cannot tell you how many times I've used them. That being said, I have a problem that has me running in circles.

1993 5.0L, Edelbrock Heads, GT-40 Roller Rockers, GT-40 Upper and Lower Intake, Stock throttle body and MAF, Ford Motorsport 19# Injectors, E303 cam (Timing Chain replaced with Cam).

The car runs fine during warm up - the popping in the intake (which happens at idle and while cruising - but does not seem to happen under hard acceleration even when warmed up) seems to start almost immediately upon the car reaching ~150 degrees (my guess is that this has to do with the car going "closed loop." I have a 195 Degree Thermostat in the car - so though I used to think the problem started with the thermostat opening, I do not think that is the case anymore.

What have I done / checked?
1) TPS is .97 at idle and 4.6V at WOT - measuring the pressure differential of the Red and the ground gives a solid 5V.
2) Good compression checks all around - does not appear to be any water in the oil (definitely not "milky" - appears clear) - the exhaust has some vapor when it is cold, but it does not linger longer than normal. When the car is not out in the cold I do not notice any water vapor.
3) Fuel Pressure. Have not checked it (I ordered the gauge to do so tonight), but the car does pull strong on the gas (the popping does not get worse, it seems to disappear) - the Fuel Pump is ~30k miles old, and the 19# injectors are only 10k miles old (as is the fuel filter).
4) Vacuum Leaks. I've looked everywhere for cracked hoses and have not found any. I've redone the gaskets on the Throttle Body to EGR, and EGR to Upper Intake.
5) Over the course of the last 18 months I've had two bad radiators - initially I thought the coolant was getting sucked in through the EGR Spacer (hence replacing the gaskets twice), then I thought it might be a bad head gasket (hence the compression checks). I still have not ruled out the fact that it could be lower intake manifold to head gaskets - though the car does not seem to be putting out an unusual amount of smoke out of the exhaust that would go with this (if it were coolant in the intake - though I guess there could be a straight vacuum leak - though I don't hear anything suspicious under hood when using a stethescope).
6) The plugs are fairly light colored - I would not go so far as to call them totally white, but they are definitely not a nice tan brown color - they are more white.
7) About a year ago I cleaned the MAF, the IAT, and the EGR. I was trying to chase down a hanging idle issue - but never got it resolved (the idle hangs slightly as I coast to a stop, then it immediately drops down to where it is set). The car idles around 750-800 - fairly smoothly (E303).
8) The O2 sensors are about 1 - 1.5 years old.
9) I drive very conservatively and get around 18-20 MPG - though it seems to be going down lately.
10) (here is the weirdest thing) The car does not have a check engine light, and no codes are popping up.
11) I have checked the timing (with the connector out) and it is spot on 10 Degrees (which I realize is conservative, but I wanted to eliminate that as a possibility).

What am I still considering?
1) Lower intake manifold leak of some sort - either coolant or air into the intake leaning out the mixture.
2) Some sort of Sensor (I'm leaning toward an O2) giving faulty readings that is feeding bad information to the computer during "closed loop."
3) Checking the Rocker arms to see if one has someone how come loose (though it seems like if this were the issue it would be making more racket - which I've listened to with a stethescope and there doesn't appear to be any - and it seems like it would be causing the issue the whole time - during warmup and during warm operation).

I'm stumped guys. I've been planning to switch over to a megashirt fuel injection computer to better tune my combination, but I do not want to complicate that by not knowing what is causing this issue. Any help is appreciated.
 

·
Registered
Joined
·
232 Posts
In your case I think Its a lean backfire through the intake, You have added a lot of good parts but now its time to add a 70mm MAF Calibrated for 30 pound injectors and install a set of 30 pound injectors, add a 65mm t/body and a 255L in tank fuel pump. This is going to help match your parts and give you a heck of a lot more power, keep your foot out of it and the gas milage will stay about the same. Then the plugs will look like they are not so lean (white)

P.S. you can lower the t/stat down to a 180 and still get good heat from the heater. The engine will love the cooler temp esp during those hot summer days..Don't go lower than 180 because the computer goes into closed loop at about 165 degrees,and the heater will be to cool :hihi:
 

·
Registered
Joined
·
4 Posts
Discussion Starter · #3 ·
Madmaxx69. Thanks. Higher output injectors (you think 30#s? I was thinking 24#s would be plenty), High Capacity Fuel Pump, calibrated MAF, and throttle body are definitely on the list - though I've read people with similar combinations to mine not "getting lean" around 300hp, which is where i think I am (actually, probably more around 280 - if it were actually running right). I was planning on making those investments right after seeing where my motor was with respect to lean-ness at the top end (after I get the MegaSquirt hooked up and can log the data).

The car seemed to not do this before, and the "popping" is under very light throttle on the highway - so I do not believe the injectors or fuel pump are at their capacity under that situation - but maybe I don't understand the system correctly.

It also just occured to me that maybe my fuel pressure regulator (stock and original) is not doing its job properly - I'll look for a test for that. Not sure how the Fuel Pressure regulator fits into the open verse closed loop issue though. Now I can't wait for that Fuel Pressure Guage to get here - I should have done that a while ago (assuming the pump is good probably not a wise move). Thanks.
 

·
Registered
Joined
·
4 Posts
Discussion Starter · #4 ·
Oh, and I found below on the Forum (thanks StalkerStang) - so I'll be sure to check both the regulator and the pump once I have the proper tool.

"You can test that with a fuel pressure guage, start and/or crank that car, turn ignition off and check fuel pressure. The guage should hold between 30-40 psi for a while, and gradually drop off over a 20 min period. If it's ruptured, it should drop off almost instantly.

That should check the regulator, othewise, idle should be around 30-35 psi. You can remove the vacuum to the regulator, (plug the hose), and it should go to max pressure (basically simulating WOT) which I beeleive is 38-44 psi for a stock regulator."
 

·
Registered
Joined
·
3,838 Posts
1993 5.0L, Edelbrock Heads, GT-40 Roller Rockers, GT-40 Upper and Lower Intake, Stock throttle body and MAF, Ford Motorsport 19# Injectors, E303 cam (Timing Chain replaced with Cam).

The car runs fine during warm up - the popping in the intake (which happens at idle and while cruising - but does not seem to happen under hard acceleration even when warmed up) seems to start almost immediately upon the car reaching ~150 degrees (my guess is that this has to do with the car going "closed loop."

6) The plugs are fairly light colored - I would not go so far as to call them totally white, but they are definitely not a nice tan brown color - they are more white.
The 19lb injectors are too small for your engine combo so the engine's running lean. If you haven't already upgraded the fuel pump, do it now. A 190lph would be good, a 255 even better especially if you plan to add forced induction later on.
Then add a set of 24lb injectors with a MAF calibrated to that injector size. Your problem will be solved and the engine will make more power.
 

·
Registered
Joined
·
45,742 Posts
Based on your combination, you could upgrade to 24's, they would be plenty, and then a corresponding mass air meter.
Don't worry about it not throwing you a code, everything that happens doesn't throw a code. Only things monitored by the computer will so if it's a mechanical problem, you won't get a code. The 1993 model isn't as computer controlled like the newer models are.
What kind of regulator and fuel pump is it using? If they're stock, you might need to upgrade those first.
 

·
Registered
Joined
·
4 Posts
Discussion Starter · #7 ·
I'm pricing 24# injectors, a corresponding Mass air meter, a new fuel pump, and new regulator . . . all of the above are basically stock at the current time. No doubt that lean is an issue, but I'm still not sure why it's only getting so bad under certain conditions . . . maybe this is one of those situations where it's better to just solve the problem and not worry about why it started 'all of a sudden.'
 
1 - 7 of 7 Posts
Status
Not open for further replies.
Top