clix813

I just replaced my IAC because I was getting a really rough idle. It fixed that but now if I have to come to a stop a little harder then normal the rpms hang up around 1200 then just drop to about 200 then it cant recover and stalls out. What could be causing this. Does the ecm need to relearn the new IAC, or does the IAC just need to be broken.

1998Slow 'Stang

Did you disconnect your battery for the 20 minutes or w/e is supposed to clear the ECM? I went through the same thing after putting in my new IAC until I reset unhooked the battery cable for some time.

clix813

Alright wasn't sure if I needed to do that, guess I should have its one of the common sence things with vehicles

Blackvenom01

if that doesnt work then i would change your TPS also

cliffyk

5-7 minutes will do it, this resets the KAM (Keep Alive Memory) and forces the PCM to relearn things like idle air, fuel trims, and the like.

You should always do his when changing anything that has anything to do with engine control. In fact I reset mine 2 or 3 times a year to deliberately make the PCM relearn it all...

Cornbread52

Also, make sure you hooked up all the hoses. That will also cause your problem.

SVTeeshirt

Cliffy, any chance a bad MAF would cause this?

If not you may have a vacuum leak.

cliffyk

It is not inconceivable that the MAF output at low rpm/idle could be far enough off to cause it--however hot-wire MAFs are largely one of those either it works or it doesn't things.

Is it the stock MAF, if not what brand/size is it?

Can you datalog MAF, spark, short term fuel trims, load, tps, and rpm while it's stalling out--that may reveal something...

clix813

replaced the tps, still kinda hangs not as bad as it did before but it still does. If I come to a stop fast enough where the rpms are above 1000 it will just stay up there and I have to keep the breaks on pretty good then if it goes below that 1000 mark it will hit about 200 rpms and then just keep bouncing up and down between 200 and 1000 trying to stay on. this seems really odd, from what i can tell there is no vacuum leak but ill look over all the hoses again to try to see.

1998Slow 'Stang

Really don't want to hijack this thread, but, Shouldn't this also make the check engine light turn off until the issue causing the CEL arises again? Mine stays on due to the post-cat o2 sensors reading funny as a result of my O/R H pipe. OR do you have to have the codes erased for it to go away?