High idle

[rchurch5945]

I posted a few months ago that my 96 tahoe 5.7 vortec would idle extremely high at times - 1200 - 1500 rpm in gear and 1800 - 2200 in park or neutral. It was very sporadic. At times it would idle normally. I got some great responses but nothing helped.

I changed the TPC and the IAC (?) and removed and cleaned the throttle body.

The last few months it has idled normally all the time, but recently has started to idle high again. I have come to the conclusion it is idling high only when the air conditioning is on. When I turn the a/c off it takes a little while (up to 15 or 20 minutes) for it to start idling normal again.

is there a switch or something that affects the idle with the a/c on? What else could it be? It's a PITA to try to drive with it idling at 35 mph!

 

[bigfootchiro]

Start by checking timing, fuel trims, voltage to TPS, IAC readings at idle, maf sensor, and for vacuum leaks

 

[exp500]

Do you have a scanner, multimeter, test light, spark tester and fuel pressure guage? If so you have the tools to find it.
Start with the cold start temp sender. What is output cold/warm?
And as Bigfootchiro said above. The more info you can gather the better the chance of finding the offending culprit !