• The site migration is complete! Hopefully everything transferred properly from the multiple decades old software we were using before. If you notice any issues please let me know, thanks! Also, I'm still working on things like chatbox, etc so hopefully those will be working in the next week or two.

Rough Idle

hacket

hacket

New member
Hey guys,

I posted about this a while back, but I haven't done anything to remedy the situation. (changing plugs or wires)

Doing a little more research this morning, I'm thinking it may be my IAC valve acting up. The car has 166,500 miles on it, so it's probably never been replaced. The problem comes when the car is idling, not during driving. The engine RPMs will go up and down slightly, and about every 1-2 seconds I'll feel a slight tremor under my butt. Obviously a rough idle.

However, I don't know where the IAC is. Does anyone think this is the problem, and if so could you tell/show me where it is?
 


Yes and.......Yes:th_thumbsup-wink:

The IAC valve is on the front side of the throttle body, round, and held on by two screws. There is an electtrical connector going to it with four wires in it. Get it from NAPA and I believe it has a lifetime warranty (with receipt). Easy 10 minute repair job.

The key is that it only occurs when idling, not driving. The IAC is there to meter air into the engine when idling because the throttle butterfly is all the way shut, so no air getting in there. The IAC pintle gets sticky and is unable to move freely causing the rough idle.
 
Wow I thought to check and someone had just posted. Thanks man I'll let you know how it goes. How's that GP running with 227K miles?
 
Googling CPS turned up 'central power supply'. Is this what you mean? Obviously I'm learning so could you explain what this is and why it could be causing a rough idle? I couldn't find a whole lot initially.

Thanks!
 
How's that GP running with 227K miles?
Click to expand...
Runs great. Oil is not even dark when it's changed. Planning on 400,000 miles plus depending on how the body holds up. At the GMPT Factory 36 reunion (where the 3800's were made) the winner had 450,000+ miles on his motor with no re-build. 200,000 miles was actually rather common.:D
The secret is that tolerances were ran "tight" during the manufacturering process and every motor was "hot tested" before being shipped. That way if there was a problem it was caught before it left the factory.
 


mystic231 said:
Runs great. Oil is not even dark when it's changed. Planning on 400,000 miles plus depending on how the body holds up. At the GMPT Factory 36 reunion (where the 3800's were made) the winner had 450,000+ miles on his motor with no re-build. 200,000 miles was actually rather common.:D
The secret is that tolerances were ran "tight" during the manufacturering process and every motor was "hot tested" before being shipped. That way if there was a problem it was caught before it left the factory.
Click to expand...


Yea they are great engines. Only thing to go wrong with mine since I got it 55,000 miles ago was the lower coolent intake gasket. Everything else is just regular maintenance or small, like this IAC.


Speaking of that I'm looking around and not finding a place to buy the part. I've looked on Napa's website and can't find anything relating to intake. Maybe I'm blind, but if someone finds a site, could you post it.

Thanks.
 
Awesome. I'll probably order it in a couple weeks. Gotta finish up my internship and get home where I have a place and tools to do it.

I'll probably write up a little how-to about it as well, so anyone looking for a rough-idle solution can find it. There seem to be quite a few about...
 


You must log in or register to reply here.
Back
Top