I had another thread for no start issues but that's fixed. So I noticed my idle was all over the place. Bounced around and wasn't very smooth. I just replaced the maf and the iac. I didnt get a chance to test anything because I noticed my water pump died. So now I have all of those items fixed and was idling the car to bleed out any air and the idle was low and smooth. After it ran for roughly 2 to 3 mins the idle jumped up crazy high. My tach doesn't work but it sounds like the idle is well over 2500. I've done the iac relearn and checked to make sure my throttle wasn't sticking but I'm stuck at this point. Not sure what else to check.

 

I like to seal off the throttle body and make sure you can stall the motor. Then seal off the IAC inlet port to make sure the RPMs drop below where the idle should be or even stall a cold motor. This just verifies air is not getting in some other way. Once you are sure you are not getting air from someplace else you need a scan tool to make sure the IAC is being told to go home. Home should be the same as plugging the inlet port. If the ECM is tell the IAC to go home and it is not dropping RPMs then either the IAC is not working or the wiring to the IAC has an open or loose connection. If the issue comes and goes it sound like a loose connection. May be a good idea to run a temporary ground to the throttle body just to make sure it is grounded.

You could try wiggling wires but be gentle. 33 year old wires are not going to like being moved too much. Upper intake gasket failure was common back under warranty for these cars. I use to see 2 a month minimum. If you did not do the IAC homing process correctly then the issue should fix itself in a few days.

 

I will try that next. I def feel like its going to be either electrical or the IAC is just a bad one out of the box. She's never had a clean idle since I've had her and the 2-3 mins of warm-up she purred. So in my mind that rules out any kind of vacuum leak. The needle didn't even wiggle on the Tach. The tach kinda works but its waaaaaaaaay off. It used to stay pegged out after you turned the car on so I changed the circuit board on the back and it works now it's just not accurate. I'm much closer to getting her running right so maybe this is the last thing for now lol. I'm going to removed the entire throttle body and clean everything really well. I'm also doing a coolant bypass because I'm in Florida and don't need 200-degree coolant running through my throttle body.

 

Are we talking Rough idle cold or high idle cold. High smooth idle means you getting too much air the only question is from where. Rough idle cold can a LOT of different things. One of the tuffest things for a car to do is idle smooth when not at operating temp. Rough idle cold can be cause by just about any system the engine uses. Even a warn motor with valves not sealing in the compression well will show up as rough idle cold first. Worn timing chain will show up the exact same way at first. Fuel pressure, weak ignition, dirty injector, leaking EGR can all cause rough idle cold. I am not saying that what its is just trying to say I would not laser focus on the Air inlet issues You will need more tests. Starting with a vacuum test.

 

pretty sure it's either the new iac is broken or the circuits for the IAC are bad. I did a cold start and unplugged the IAC. She ran decent enough. She did idle up a hair but nothing drastic. I plugged the IAC back in the idle skyrocketed immediately.