ive researched this and i continue to have contrasting results. many people say that my iac valve is bad, the shop ive been bringing it to says its something wrong in the wiring harness. here is the issue

its an 86 camaro 305 tpi, and has a t5 in it. when i disengage the clutch and therefore take a load off the engine, it bogs down and dies, when i give it gas it works fine. something is choking my engine.

when i come to a stop it may rev up to 1500 for a minute but then hovers around 1000-800 and may die or may not. when it starts up it goes straight to 1500.

do any of these sound like symptoms of a bad iac valve? maybe one that cant keep up?

any input would be greatly appreciated since my next step is going out to buy the $90 valve, thanks.

Eric

 

i have seen pretty much the same issues with a dodge stratus with Automatic.. When you take your foot off the gas it would die just driving down the road.. It would run fine but idle off a little.. It tunred out to be the IAC.. I've heard you can remove and clean them you could try that first if you haven't already... We cleaned the dodge IAC but still had to change it before it worked..

 

how old are your runner gaskets? sounds like a problem I had when a small wire got sandwhiched between a runner and the mainfold and I didn't see it. Car had the same problems until I tore the tpi all the way back down and found the wire. A bad runner gasket would cause the same issue
. Unmetered air in the system.

 

..

 

I agree with iroc m and huke

I think what Irocm is getting at is that it can be a vacume leak.
and Iac's are known to cause bad idle too. I'd treat the the throttle body /plate to a good can of tb cleaner paying some attention to the iac port then change the iac.

 

okay so update on everything. the iac is NOT the problem, i replaced it as well as cleaned the throttle body with carb cleaner, still screwing up

there is an odd pattern though, the car runs BEAUTIFULLY when its cold. no complaints at all. as soon as it heats up it starts stalling every time i take a load off the engine.

any thoughts? a short maybe?

 

Possibly a short. Possibly an issue with the coolant temp or manifold air temp sensor. Has anyone had a scan tool connected to the car when this was happening to look for strange data?

 

Acting up when warm is a sign of an ignition module problem. Also, you better ohm your injectors to make sure they are all good.

 

Good call ninetyone. Injectors that are starting to go are affected by heat as is a weak ignition module. Either one could possibly produce your symptoms.

 

this all started happening right after i got my intake manifold done, is there anything that would have been removed and reinstalled wrong that would cause this?
its the reason why im iffy on having bad parts. i will check the ignition module and injectors though.
question: if my injectors are bad would they still fire fine when i give it gas?

 

No, not so likely. Generally, we look to injectors or fuel supply when there is a problem at wide open throttle. You could have an intake leak between the cam valley and one or more intake runners. As I said in my first response to you, connect a scan tool and look for odd data. Does, BLM go high when the problem is occurring? that could point to a vacuum leak. Smoke test the intake, with both PCV valve and make up air line out of the valve covers and plugged, and look for smoke coming from the PCV opening.

 

I guess some good questions would be what tools do you have available to you for diagnosis? Do you have any spare parts to swap around to check things?
The scantool is the best idea right now. You can get them cheap. I have an actron and it helped me diagnose a computer problem. The CTS and IAT were new but the scanner showed them to be way off. No SES either. New computer fixed it. My actron has to be set to an 86 5.0 MPI to work but it works fine. There are so many things that could cause this you need to establish what is good and what is not. A broken fast car is not worth much without the tools to fix it. Let us knwo what you have and we can point you in the right direction.

 

My car would do the same as u described. I found the throttle position sensor was bad. replaced that and the surging idle and stalling went away.

 

That makesd sense. Should have thought of that. Sweep test the TPS using a volt meter. DVOM will work. Just sweep the throttle very slowly while measuring voltage between pins A & B. You'll need to sharpen a couple of paper clips to use as backprobes. Watch for the voltage reading to change irratically around closed throttle. Always double check your results to be sure you dont have a bad connection on the test leads.

Since the problem seems to be worse when the engine is hot, be sure to test under the same conditions as when the problem occurrs.