I have a 89 GTA with the 350 TPI. When it's cold and first started, i get a rough idle. After about 3-5 minutes of idling, it will all of a sudden just click and idle just fine. The car has sat for a while now, but it was doing this before being parked. I had already done a tuneup then and it still does it. I know it's due for another tuneup now, so i was wondering if anyone knows what might be causing this so when i get the parts i can go ahead and get everything i need at one stop.

Oh, after it has gone thru this time, it runs fine and will start fine until it sits over night. Haven't noticed it do this after sitting a few hours while being out or something. Seems it has to sit for a long while, like over night. Any info would be greatly appreciated. Thanks

 

Nobody has any advice? lol

 

You obviously have a cold-start issue but you need to elaborate on "idles rough". Does that mean it surges? Idles too high? Idles too low? It's missing?

Also, is this engine stock (heads, cam, etc)?

Providing more detail will help us diagnose the problem.

 

Ooops, my bad. I thought i had more info in here, i must have thought it but didn't type it.

Ok, when first started after a night of sitting, it's idle is rough and low. If i feather the throttle i can get it to idle up and hold, but it's missing/skipping. If i don't feather it, it will bog down and shut off. I haven't noticed if it's running rich or not since i'm sitting in the car feathering the throttle. It does smoke at first start, but i know that's the valve seals. It is all stock. I haven't tried to drive it this way, i just let it sit and warm up to the point when it clears up and it'll drive fine from there. Even after sitting a few hours, it's fine. But over night is when i really see the issue come back.

Sorry for lack of info again. I thought i had put all that in here.

 

No problem. These cars are notorious for idle issues. Truthfully, there are many things that can cause a bad idle so it takes some time to determine the source of the problem.

I would start with cleaning or replacing, if necessary, the Idle Air Control valve.

Have you checked the fuel pressure, at the fuel rails, with a gauge to ensure it is steady?

It is also possible you have a malfunctioning EGR valve (assuming your EGR is still in place). These can cause a vacuum leak if bad.

Let me know what you find and we can go from there.

Hope this helps!

 

I appreciate it. It'll probably be this weekend before i get a chance to really get into it. I think i may have a gasket leak at the intake from the plenum. Not 100% sure on that yet. When i had it running, if i throttled it up, i could see like a puff of smoke that would go away almost immediately. At first i thought it may have been something electrical, but it's consistent when you tap the throttle up. Can't remember if it puffs on the way up or coming back down to idle. But, it's been acting this way long before that has come up.

So, i will get into it this weekend and check some things out. The car is still stock and has the egr still on it. My truck had a bad egr valve and this doesn't really feel the same way, but i know they can make things act differently. I'll get it all checked and cleaned and see what happens. If i clear it up, i will post what it was as well. If not, i'll be back. lol.

ETA: If the gasket was leaking at the intake and plenum, would the idle change if i sprayed carb cleaner at it? I did try that to see if it would idle up, and it didn't. But i'm not sure about the TPI system and if that's a spot that would cause it to idle up when sprayed.

 

if you have a MAP, a leak would cause a high idle. it reads pressure, not airflow. reset your idle, and make sure the tps is set right. but first clean ur iac valve.