SunBird 94

My GF owns a 94 Sunbird that randomly doesn't like to start. Sometimes it'll start up and run perfectly, other times you can crank it and crank it without it starting. Give it a little gas and it'll start, but let off the accelerator and it dies instantly. It has the most trouble when the motor is warm although it won't start cold sometimes too. I've had it on the scan tool and noticed when the car starts on it's own all the parameters read great and nothing is out of the ordinary. When you have to force it to start, most parameters are good except the fuel trims are real rich, which you can smell in the exhaust, and the IAC position is real high. There are no vacuum leaks, base fuel pressure is 37-38psi, car has good spark, new IAC, and the egr has been blocked off for diagnosing the problem because the valve is stuck open allowing rich exhaust gas into the intake during idle. I thought maybe the fpr was bad, but there is no sign of fuel in the vacuum line (hence its leaking) and it seems to hold pressure in the system after the car is turned off. any help is greatly appreciated.

heatherannie22

Did you run a code test? sounds like it might be an oxygen sensor.

SunBird 94

No codes.

I don't suspect the o2 because it showed a good voltage readout and was crosscounting on the scanner.

thecommi

check the ignition module?

Overtime

Does this year have a MAF sensor? You can clean it off with carb cleaner and see if it helps or replace it.

SunBird 94

This car is one year prior to the MAF.

Took the module out last night and had it tested at NAPA. Everything checked out 100%

I replaced the ECM just this afternoon and it fired right up the first try. Tried it two more times and it wouldn't do a damn thing.

I am at a total loss.

RABarrett

Typically, when fuel trims are very rich, it is due to the baro sensor, (MAP) is causing a problem. Is this reading correct when the engine refuses to start? Is the sensor reading and the ECM reading the same? Start there. Ray

SunBird 94

I tried the MAP out of my friends chev pickup with no better results.

I do have some good news though, I found a problem with the wiring going to the ICM. It was starting to become brittle causing a poor connection. I fixed it up and ran some errands, starting it up over 20 times without any difficulties. It seems logical thought with the cars mileage and not to mention the drastic season changes in Minnesota!

I'll keep this post updated should anything change. Thanks for your input.