more rpm/idle problems

[05GM123]

last time i posted my car would idle high any time it was in drive once i left off the brake. I had my throttle body cleaned and reinstalled my tune. This seemed to fix it since the car has not had any problems the past week or two. Well now the driving part is fine but when I start the car the rpm's shoot up from 0 to 3000 and proceeds back down to 50-150 (basically the needle goes all the way down). After it sits that low for a second or two it gets back to around 500-750 (my tune is for a 750 idle). This only happens upon cold start and after driving for about 3-4 minutes and everything warms up it idles fine and starts better but still goes low (around 500 rpm).

Is it possibly a bad IAC or is this something new?

[Jeffonebuck]

Any codes?

[05GM123]

No codes and no lights

[Jeffonebuck]

Have you cleaned your MAF, dirty sensor ?, Vacume leak, maybe bad reading from O2,?? Did you reuse old gasket when you took throttle body off and cleaned it. When was the last time plugs, fuel filter were changed.?

[Marauderjack]

What "tune" are you running??:confused:

Try disconnecting the negative battery terminal for a few minutes to reset the Adaptive Learning feature....that usually fixes mine when it acts weird!!:beer:

Good Luck!!

[fastblackmerc]

IAC... clean it.

[loud2004marquis]

+1 ^^^what he said^^^

[05GM123]

I didn't clean the throttle body or work on it before, my shop I use just tried to get some of the grime off of the throttle body; they didn't even take it off. I currently have Zach's tune on right now.

Started getting some codes this morning when I drove it.
P0172
P0175
P1132
P1152

I already searched on MM what these codes mean and seems to probably be 02 sensor or EGR problem....agree? My mechanic is taking a look at it tonight or tomorrow hopefully with some news.