Idle question
Joined: Nov 2001
Posts: 34,631
Likes: 2,557
From: Schiller Park, ILL Member: #317
Does it stay at 1300rpm for an extended time? Or does it recover to 800 after a few moments and stay there? A sudden jump when the A/C is flipped on is normal, so long as it returns to normal idle speed shortly after.
If it stays at 1300 even after driving and coming to another stop, then there is an issue. Most idle hang issues on stock cars are caused by either a vacuum leak of some sort, an IAC valve issue, or throttle linkage binding. If the car is throwing a code, scan it and start there. Also, if you have access to a scanner you can check fuel trims as well to help identify a vacuum leak and possibily point you towards areas to inspect depending on what the trims show. You can also scan the TPS voltage and TPS angle percentage to point you towards any possibile linkage binding.
If not, then I'd pull the IAC valve and clean the pintle and the bore, also check the throttle cable for smooth operation and that it fully releases/allows the TB blade to close fully. And finally check for vacuum leaks in/around the TB/bellow/MAF, intake, EGR-to-intake tube, PCV system, etc.
Hope that helps.
Edit: Just noticed that you list "MAF" as a mod. Ported stock MAFs have been known to lead to idle issues for quite a few people. Maybe try a 100% stock MAF and see if the issue goes away.
If it stays at 1300 even after driving and coming to another stop, then there is an issue. Most idle hang issues on stock cars are caused by either a vacuum leak of some sort, an IAC valve issue, or throttle linkage binding. If the car is throwing a code, scan it and start there. Also, if you have access to a scanner you can check fuel trims as well to help identify a vacuum leak and possibily point you towards areas to inspect depending on what the trims show. You can also scan the TPS voltage and TPS angle percentage to point you towards any possibile linkage binding.
If not, then I'd pull the IAC valve and clean the pintle and the bore, also check the throttle cable for smooth operation and that it fully releases/allows the TB blade to close fully. And finally check for vacuum leaks in/around the TB/bellow/MAF, intake, EGR-to-intake tube, PCV system, etc.
Hope that helps.
Edit: Just noticed that you list "MAF" as a mod. Ported stock MAFs have been known to lead to idle issues for quite a few people. Maybe try a 100% stock MAF and see if the issue goes away.
Now that's what I call a thorough answer! With the A/C on the idle will change when I come to a stop. Sometimes it drops back to normal other times it will go to 1100 rpm.The problem just started this past week. I ported my MAF about 3 months ago. Maybe it took this long to cause an idle problem.My MAF still has the screen in and I did not cut out the plastic around the wires.
Joined: Nov 2001
Posts: 34,631
Likes: 2,557
From: Schiller Park, ILL Member: #317
Very possibile that it might have just taken some time for the physical MAF change to settle into the PCM and cause tuning issues. See if you can get ahold of a stock MAF, install it and reset the PCM and see if the issue returns.
Lots of things can cause intermittent idle issues, I've spent MANY hours hunting these issues down on some of my own cars, including my '98 LS1. I had an extremely intermittent idle hang on my Z28 this spring, after trying/checking/scaning/replacing almost everything I could think of, it ended up being the EGR valve in the early stages of failure. The valve wasn't bad enough to set a code, but I did get a high idle DTC once. Not saying that the EGR is your issue, could be a dozen other things, but in my case that was the final part that I replaced and that's what did the trick. It's always the last thing you try, aint it?
Lots of things can cause intermittent idle issues, I've spent MANY hours hunting these issues down on some of my own cars, including my '98 LS1. I had an extremely intermittent idle hang on my Z28 this spring, after trying/checking/scaning/replacing almost everything I could think of, it ended up being the EGR valve in the early stages of failure. The valve wasn't bad enough to set a code, but I did get a high idle DTC once. Not saying that the EGR is your issue, could be a dozen other things, but in my case that was the final part that I replaced and that's what did the trick. It's always the last thing you try, aint it?
Joined: Nov 2001
Posts: 34,631
Likes: 2,557
From: Schiller Park, ILL Member: #317
LOL. 
I must be overly tired. How could I have missed it, you have an '02 LS1. You have no EGR system. Disregard everything I said about EGR system checks. At least that's one thing you can cross off the list of suspects!
Sorry about that. For some reason I though you listed an '00 car in your sig. My mistake.....
I must be overly tired. How could I have missed it, you have an '02 LS1. You have no EGR system. Disregard everything I said about EGR system checks. At least that's one thing you can cross off the list of suspects!Sorry about that. For some reason I though you listed an '00 car in your sig. My mistake.....
Thank you for your help! This weekend I will go through your list of possible problem area's after I put in my new tranny mount and UMI LCA's. Funny though, today I ran the A/C and didn't have a problem, the car idled fine.
