97 Bonneville 3.8 natural. On cold start engine revs between 500 and 200 rpm repeatedly till it stalls out. no dtc showing. what should I be looking for ? also on code check it says EV not complete and Oh not complete. Any help would be appreciated. Thanks

Sounds like your IAC(Idle Air Control valve) is sticking/closed too much. Maybe even bad.

Try cleaning the pintle with some carb/choke cleaner. I can't believe we don't have a thread on how to clean it. But we do have a thread on how to remove it...

https://www.gmforum.com/normal-maint...cement-284339/

Thanks for the quick response. I will check that tomorrow

Mike I have done a few IAC cleaning posts of which I could find this one quickly.
https://www.gmforum.com/buick-172/in...avenue-304014/
I should do a proper one for mechanical sticky or something if u like...
Showing more steps like including where I use an old tooth brush etc in process and a more detailed step by step etc...
Would not take me long to add some more pretty pictures with tools being used in removal too, as I am due for another IAC cleaning maybe even next weekend... I can make it so.

That would be fine Art. Just start the thread in the Gearhead section, and we'll work it from there.

Acknowledged.
I will attempt to "shoot" for next weekend then.

Mike I installed new the IAC motor . No changes. On cold start -25C engine still surges until I put it in drive then it stops. I put a diagnostic report in my photo album. Any help would be appreciated

that is your readiness monitor status, doesnt really say anything about the engine.

did you clean the throttle body were it seats? surging can also be caused by a vacuum leak

cleaned area well. If it were to be a vacuum leak would it not surge all the time? I understand they are readiness monitors but it has been like this for a year. I can't complete the drive cycle

How about cleaning your MAF sensor? Grab a can of MAF sensor cleaner(right next to carb/choke cleaner) at Autozone and the like. Remove it from the TB, spray, reinstall and see what happens.

Are you able to scan for any codes?