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Discussion Starter #1
I have a 1989 foxbody with a 5.0L and Im having electrical problems. First off mods consist of heads, cam (B303)and intake, and rockers. When i got the car it had no O2s and also no wiring harness for them either. I purchased 2 bosch O2s and a harness from latemodel. When i plugged them into the car it now surges very bad at idle 1100-1500rpm. Tried pulling the codes with 2 different scan tools, one from oriellys and the other is a snap-on, the car will not communicate with either one of them. With this being said i pulled out my wiring diagram and started checking all sensors and relays. I found that the fuel pump is directly wired to a "key hot" wire by the tailights and the inertia switch is bypassed, and i know neither should be this way. I also discovered the fuel pump relay under the hood was bad and i replaced it, it now works. However the relay under the seat will not work, even though it is good. Also while the car is at idle if you press the clutch the idle falls to around 900-1000rpm and the check engine light flashes on and off. any ideas?
 

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Sounds like shade-tree wiring + a possible bad computer. I'm sorry bro, sounds like a nightmare.

Try pulling your codes this way using a jumper wire and watching the CEL. I like to use my cell phone to record it so I can double check the codes.

DIY KOEO/KOER/Cylinder Balance Self-Test Procedure
 

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Computers rarely go bad.

Check all your grounds, there's one on the lower intake, one in the car by the computer, and maybe a couple others related to the engine harness.

The only way to condemn a computer is to verify that all power and grounds are good, and that it has good inputs but bad outputs. Check all the powers and grounds to the computer, and all the wires for the diagnostic connectors, then you can start pointing fingers at the computer.
 

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Computers rarely go bad.
I did say possible, damnit :shigrin

Did you ever try pulling the codes using the CEL?
 

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sometimes these are tuned in closed loop which requires no 02. If they removed the blower to sell it, then it doesnt mean they set it up correctly, Make sure the ECm has no chip in it and that the inside shows no burns or corrosion. Check fuel pressure, vacuum lines for leaks, TPS postion etc.
 

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Discussion Starter #7
I found yet another relay that was above the computer in the kick panel, it too was also bad so i replaced it. Also I tried pulling the codes with a jumper wire after i installed the new relay and it was flashing some codes. It was getting dark last night while i was working on it so Im going to stop by my parts store and get a scanner to try and pull them. Anyone have any input as to why the CEL goes off when the clutch is pressed? Im thinking the switch could possibly be bad because it shares the same grounds as several of the sensors.... thank you all for the input....
 

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Discussion Starter #8
I replaced the EEC relay and the fuel pump relay. Because the CEL would go off and the engine would smooth out and run greaat when the clutch was pressed to the floor, I pulled my clutch safety switch out and jumped it with a 5amp mini blade fuse....now the car runs like a champ and it also connects to a scanner. I believe something was a wrong with the switch...it still allowed the car to start, however it was loosing its ground after the clutch was released. (it shares the same ground as several sensors.) Thanks for help guys!!!!!!
 
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