I disconnected the battery from the computer to reset it. It took several cranks to start it and stay running. Then after a few minutes it settled out and idled ok. I started it the next day but now the idle wander's real high then real low and doesn't seem to want to settle out. It sprayed carb cleaner looking for leaks and found none. Does it just need to be driven or what? Base timing was set to 8 btdc. IAC was cleaned and lubed. Has fresh gas, plugs, filters, wires. TPS is .54v. Minimum idle still has factory plug. I feel like I am missing something...

 

Cause the 02 sensor we use doesn't work till its heated up...... Engine has to run to heat it.

 

What does the O2 have to do with a cold start idle?


IIRC stock base timing is supposed to be 10*. Is your IAC set correctly? I had mine set incorrectly and it would never idle right.

 

I will set timing to 10 and try again.

The IAC was reset by turning key on, jumpering A to B, unplug IAC, key off, plug in IAC. I didn't find the procedure in the factory shop manual but gleaned it from 3rdgen. Is it correct?

 

What are some possible problems when the idle learn doesn’t stick? Or maybe I just don’t understand… Here’s what I’m doing: I let the car sit and learn idle without touching anything for 25 minutes (fan cycled on twice) per reading other threads. I took it for a 10 minute drive then shut it off and restarted with no issue (the idle was remembered). The next morning (45F) I started it and it went back into the idle learn mode (dying after cranking). Is this normal? This is my first 2.8 MPFI so I don’t know what to expect after the battery is disconnected other than it takes several crank attempts and many loops of 400<->1200 RPM’s before the idle is learned. I have 2 ECM’s, 1 reman and 1 original, and they both do this. I’ll double check that the ECM still has some power with the key off.
I have a shop service manual but so far I haven’t been able to find anything about idle relearn or what to expect when taking the car for a drive after resetting the ECM. Is there any “official” information?
Thanks!

 

The 2.8l 3rd gens don't have an idle learn.

Being a MAF ECM the slightest vacuum leak or leak post MAF will cause idle issues.

RBob.

 

I did not know that. Thanks for the info! I'll look for leaks tonight!

 

Had mine over 15 years now, have done n chaged everything under the sun, 3-4th ECM, different chip, when cold it idles high and rev's up n down on its own, once its warmed up and all the sensors are working, its idles as normal.

 

Found something interesting. After a few attempts of cranking, starting and slowly dieing I discovered that disconnecting the IAC had no effect on the problem. The rpm still cycled back and forth from 1200 to 500 until it warmed up. I was assuming the iac was controlling the rpm.

I checked/blocked each vacuum hose. Sprayed carb cleaner all over the intake. Maybe the egr leaks? I'll block that off next...

 

Found an air leak around the egr shaft by blocking off the egr tube at the throttle body. Which smoothed out the idle. Then I removed the egr blockage and started spraying carb cleaner around the tube then inside the actuator. Makes sense because as the engine heated up it would run better. The shaft probably was sealing better hot. Time to buy an egr.