My car when you let it run at constant speed and then come to a stop the car will idle at 2000, if you turn it off and turn it back on it idles back to normal for a while then does it all over again. I have replaced the IAC and clean the TBI religiously since I run with a open filter but this only happens when the car get up to about 150 degrees. When its cold it idles just fine and for about 20min after but when it gets to 150 it starts idleing high and not going back down till I turn it off and restart it. What could be causeing this damn thing to keep doing this?

 

Water temp sensor for the ecm may not be sending correct reading to the ecm. Have you checked you tpi voltage?

 

do you mean TPS? and what voltage should I be getting out of it?

 

(tps) voltage should be .5volts at idle position and approx.4.2volts at wot. Check with engine not running. Should be gradule increase from ldle to wot