High idle issue...
 

I have a 95 Z28 Camaro. For a while now I have been having a high idle issue. The car was idleing at about 1500rpm. I was told by a few people that the IAC valve might be messed up so I took the throttle body off and tested the IAC like the Chiltons manual says to. The Chiltons says you can use an ohm meter and connect the left two pins and then the right two pins together and check to see if the resistance is between 40-80ohms. Mine was reading 52-53 on both sets of pins. I was also told that you could plug the IAC motor(once its out) back into the wiring harness and turn the car on to see if the IAC valve operates. I don't know if they meant to turn it to the on position or to actually try to start it so I had someone help me just turn it to the on position while I was holding it watching it. Nothing happened and I thought maybe it had to be grounded so I pressed part of the flat face on a couple different grounds and had my helper do the same thing. Still nothing. A few other people said it wouldn't work like that so I put it back together. I used throttle body cleaner and scrubbed all the carbon build up out of the throttle body with a rag and cutips. It is super clean now. I replaced my cracked air intake elbow, and replaced the throttle body gasket. I put it back together and now it idles at 2000rpm and kinda chugs every 5-6 seconds. I also found a metal line on the intake manifold that I think was leaking. It runs from under the throttle body to the driver side of the intake manifold. The part that plugs into the manifold was real loose so I took it out, cleaned it, RTVed it, and put it back in real snug. I have checked all the vacuum lines that I can see. I was also told you can use carburator cleaner or throttle body cleaner to check to see if the intake manifold or vacuum hoses are leaking. I sprayed throttle body cleaner all around the intake manifold, intake hoses, vacuum hoses and secondary air stuff and nothing happened. At this point I'm stumped. I just don't know what else it could be. I don't think it's a vacuum leak. I am starting to think one of the sensors is going bad. The SES light is not coming on though so I don't know what it might be. I figure either the TPS, IAC, or MAP has gone bad but I don't know how to check those correctly.

Any help would be greatly appreciated!!

Well I just replaced the IAC. Same problem. Still idleing at 2000rpm. What is the best way to find a vacuum leak? I could really use some help with this.:cry:

If anyone has a clue, I'd be greatful!

Yes a vacuum leak will cause that. Now where it IS LOK.

Oil the butterfly rod where it enters the TB. After I cleaned my TB my rpms would hang. Lubricated the rod and cured the issue.

The butterflies are not sticking and they are closed all the way when it's off. I haven't tried looking at them when it's on cause I'm not sure it will run with the intake elbow off. I don't know if the TPS can turn the butterflies or not. No one will tell me that. Assuming it cannot, there is nothing wrong there. If it can though then that is a different problem and I don't know how to check the TPS.

Does anyone know how to test the TPS?

the tps will not turn the butterflys, start the car and listen under the car for a rushing air sound, if that does not locate the problem you can spray some carb cleaner in short bursts in different areas and listen for a change in idle

Well I half way figured out what the problem is. I was given the brilliant idea by this guy ( www.bfranker.badz28.com/fbody/Guides.htm ) to take a piece of tape and plug up the IAC valve intake side port and start the car to see if it will idle. Obviously if it stays on there is a vacuum leak somewhere. If it dies then something else is wrong. I did that and it was bucking and jumping a lot but it would idle at 600rpm between sputters and bucks where it was trying to stall out from lack of sufficient air. So I know it has a vacuum leak but I'm not sure how to locate it at this point. I'm thinking about plugging it up again, then spraying carb cleaner around the engine instead of throttle body cleaner to see if that will show me anything. Instead of it idleing up like normal I think with the IAC plugged it should stall the thing out by doing this.... that is if I drown the spot that is leaking. I'll let ya'll know if this works.

If anyone has a better idea I'm definitely all ears!