I have been having this Idle problem for quite sometime. My car stalls out when put into gear if you dont give it gas sometimes. I was told it was the IAC so I replaced that and it seemed to help a little bit but its still not acting right. Could it be my Idle is not set right? Right now the only way I can keep it running is if it Idles in park around 1500 rpm and then goes down to about 1200 or so and idles in gear around 1000 rpm. It seems fine if I keep that really high idle however the car jerks when put in gear cause the idle is so high. Also If i turn on the AC the car usually cuts right off unless I keep giving it gas. Ive tried resetting the Idle several times by grounding the two ECM ports, unplugging the IAC, Adjusting the Idle screw, Removing the Paper clip from the ECM module. starting it up. Am I doing it wrong? Could it be a possible I have a head gasket leak? Any help is much appreciated Thanks guys.

 

The engine will usually drop a little bit because of the added load of the AC system. That is indeed to high of an idle. Does your computer actually amke your IAC open up? Does it do it when thoroughly warmed up?

 

It does it at all temps. When you first put it in gear it will idle fine for about 30 seconds or so and then the idle will start to get rough and eventually cut out if you do not give it gas. I know the Idle is supposed to drop when the AC is on but my engine tottally cuts off when I hit the AC. I noticed on the IAC connecter some of the plastic pieces that wrap around the metal prongs have broken off, Could that be causing a problem? All the Vacum lines are connected and or Capped Off. I removed the charcoal canister and when I did there was some sort of sensor with 2 wires plugged into it, could removing that cause a problem? I am stumped

 

Any ideas?

 

I am having the same problem. Did you ever figure out what the problem was?

 

I have been having the same problems.. you should follow the factory manual on instruction to set Min low idle 1st (which requires to disconnect the IAC during setting and then reconnecting before startup) and then check the TPS setting. You should be able to also search and find the correct method to do so.
I also have found that my Fuel Regulator was faulty and causing so High Idle at times. On unplugging the vacuum (full fuel pressure), I fould my Idle would return to normal. I would get a fuel pressure gauge and do the Fuel System Checks along with checking for vacuum leaks.

 

Mine is doing approximately the same thing at the moment, but in my case, it is because the throttle is sticking slightly open. took me a bit to figure it out because if you run the throttle by hand you tend to let it slam shut, but with the pedal it closes very lightly. I guess I'm gonna have to take mine apart and try to figure out what its catching on.

 

Yeah.. my Throttle was sticking also.. after taking it off and inspecting it.. I then found carbon and gunk in the throttle bores, vacuum ports and everywhere.. I have since took it apart and soaked it in bucket of carb cleaner, replaced all of the gaskets and IAC valve.. It function much better.. and there is nothing to rebuilding a Throttle Body.. (way easier that a Carb).

btw... this is for mr 88' TPI Vette.. Z28 is still carb.