Cold idle problem

I'm new to this forum so I'll start by saying "Hi folks...how're y'all doin'?

I recently bought a 1989 Camaro RS with a 305 TBI and 700R4. The car runs good after it warms up...BUT...when I first start it up it idles really high (1600-1700 rpm) until it warms up, then idles around 700 rpm which seems normal. This is extremely aggravating as you can guess- the car will go over 15 mph without even touching the accelerator. After it's warmed up it runs fine except when turning the engine off and re-starting. It wants to run at about 1700-1800 rpm for about 5 seconds and then drops down to the normal hot idle speed of about 700 rpm.

What is causing my problem? I've looked for vacuum leaks but so far found none. I took the IAC off to see if it was gunked up, but it looked OK. I'm going to change out the temp sensor tomorrow to see if that helps. Does anyone have any ideas on how to diagnose and fix this problem?

Thanks for your help.

Mike

welcome to the forum mike

Did the IAC have some movement in it? it might look clean, but it should be able to move in and out a little bit.. ide check it again..

After that, ide say a misadjusted or bad TPS sensor

No, as a matter of fact it had NO movement in it. I thought that it should probably move in and out, but not knowing for sure I just cleaned it up a bit and put it back. I was told to take it out and make sure that it was not gunked up...it had a very slight carbon buildup but nothing serious.

Do you think that the IAC could be my problem? I priced it at Advance and Otter Zone and it's around 65 bucks...not too bad if it'll fix the problem, but a little bit pricey to just try in the dark. I thought about replacing it to see if it would correct the problem, but decided not to until I had a reason to suspect that it was bad. It sounds like you might have given me that reason since it won't move in or out.

If you think I should replace it what do you think about the AutoZone or Advance Auto Parts discount store type products? Are their sensors OK to use or should I go to a NAPA or other quality parts supplier for this part?

Thanks for your advice.

keep in mind that it shouldnt move easily.. it should take a little effort to push it in and out..But before you replace anything, try to loosen it up.. hold it upright, so the pintle is facing up and spray some carb cleener on it.. let it soak for a while and keep spraying it.. than tap on the pintle with a hammer or something to break it loose..

WHen mine stuck, I slammed it against the concrete and problem solved.. It worked like a charm after that.. But im not suggesting this? my brother tried it, and smashed his IAC to pieces..

a good way to check it is to pull it out of the throttle body but leave it plugged in, then have someone start the car. the pintle should move all the way out

thats normal operation, the car is warming its self up to operating temperature, its a byproduct of emissions. the longer the car runs cold, the more emissions it puts out. so they set the computer to run at high idle untill it reaches operating temp and then it goes to 700rpm. both my camaros do this.

Hey 89IROC, do both your Camaros cold idle as high as mine...about 1700-1800 rpms?

Mine takes several minutes before it drops down to normal. It would be nice to know that this is just normal operation, but I've never seen any other vehicle that cold idles so high.

I tried your suggestion DaMoNe6969 and my IAC did move in and out (took quite a bit of force though). I sprayed some cleaner in it and moved it in/out a few times. It appeared to work OK. I put it back in and nothing changed...same symptoms. I appreciate the tip though.

4onFloor, I'll try your suggestion next time I get a chance to work on it. I assume from your suggestion that the engine will run with the IAC removed from the TB. It seems that it would have a major vacuum leak and wouldn't even start up due to the mass of unmetered air entering the intake tract. I'll try it and see what happens...after all I'm in the middle of a learning curve here.

Thanks guys.

mine takes several minutes before it drops down to normal. It would be nice to know that this is just normal operation, but I've never seen any other vehicle that cold idles so high.1800 RPM is no problem. When it's cold out my 91 idles at 2000 RPM then slows to 600 RPM when the water temp reaches 140. My 78 idles at 2500 RPM when cold (a mechanical throttle positioner does this)..§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§REFUSE TO LOSE§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§

like i said, normal operation. nothing wrong with it.

4onFloor, I'll try your suggestion next time I get a chance to work on it. I assume from your suggestion that the engine will run with the IAC removed from the TB. It seems that it would have a major vacuum leak and wouldn't even start up due to the mass of unmetered air entering the intake tract. I'll try it and see what happens...after all I'm in the middle of a learning curve here.

Thanks guys.


the car will run like shit, but atleast you'll know if the IAC is working. yes you'll have a big vacuum leak, but the pintle should move out as if it's restricting air flow into the throttle body trying to correct the mixture

OK guys, you've finally convinced me that nothing's wrong with my cold idle speed. I'll stop worrying about it (after I try 4onFloor's tip and make sure the IAC pintle is moving out on it's own).

I appreciate the help and the persistence it took to convince me there was nothing wrong. I have a couple more problems with the car that I'm gonna eventually ask for some help with. It's nice to find a site where the members know their shit!!

glad to help.