I have a 91 Z28 with the tpi 350 that idles smooth but high (1000-1200) when cold. After a few minutes it drops down to where it should be at about 600-750 in drive. This has been going on for a while now and its getting really annoying since at stop lights my torque converter is loaded up which makes it harder to stop and is wasting gas and puting componets under stress when they dont need to be. I already reset my iac and my tps several times and nothing changed. Also checked for vacume leaks and still nothing. Any ideas!!!

 

That can be completely normal, depending on coolant temperature. If the air is a little cooler than normal, you may not have a problem at all.

The fact that the idle RPM drops to normal after the engine is warmed up indicates that the IAC is working just fine. If you suspect that the situation is not due to cooler weather, you can test the resistance of the CTS at a known coolant temperature.



If the resistance readings appear normal, you can compare them to the sender for the temperature guage on the dash, since the resistance/temperature scale is the same. You might also want to check the connectionos for the CTS, since teh sensor is only part of the circuit, and higher resistance from poor connectiosn will result in a lower temperature indication to the ECM.