I've been working on a 1985 Camaro 5.0 tpi auto. So far I've put on intake gaskets, iac and an egr valve and it's running good now except for when you first start it up it will idle at about 1500 rpm's and will not slow down until you put it in gear and drive it about 40 to 50 ft then it will idle down to where it should be. It doesn't make a difference if you let it idle for that distance or if you give a little gas. If you let it set and idle for a while after it warms up it will then repeat the above process. I don't know if it does this before Thanks in advance for any help.

 

I have got the same problem. After a couple of months working on the car i started it yesterday. No codes but idle at 1500 rpm. The car is also a 5.0 tpi. Maybe this occurs because the ecm is reseted.

 

87 camaro iroc-z I adjusted my tps and problem went away. You might give it a try.

 

if ur car is below a 1990 then u need to properly set your IAC AND TPS https://www.thirdgen.org/tpimod2S.