07silverc6

Any ideas on the 1500 rpm idle hang? Cleaned the T-body and maf and now it hangs at 1500 rpm's until til the car comes to a dead stop. Any ideas how to fix?

ffastwheels

have the same problem and no one has a real fix it.....I did the same as yourself and it still does it...I guess it will need a tune and a throttle re-learn.....

schpenxel

Min airflow is an obvious first thing to mess with tune wise.

Ensure there are no vacuum leaks as well

07silverc6

No vacuum leaks.

ffastwheels

haven't found any leaks even tried a smoke test so that one is out of the equation....MI AIRFLOW means what exactly....

schpenxel

Table that controls how far the throttle blade closes basically

ffastwheels

when the car drives for a while it idles at about 1500 rpm when the clutch is depressed and the car is still moving....as soon as you come to a stop 2-3 seconds later it goes back to its normal idle so I don't think the throttle blade is off....would it not do it continously if that was the problem....it's been doing it for a couple of years now....it's frustrating because it doesn't do it all the time.....

JRE-C6

When I supercharged my C6, the great folks at A&A told my tuner to adjust the idle cracker to eliminate the idle hang, and that solved the problem.


Jim

ffastwheels

I have novi 2200r in my garage but I haven't installed it yet when I do I'll make sure the tuner is aware of the problem....thanks for your response drive safe

schpenxel

But you also don't know that adaptive idle kicks in once you're under about 1mph which gives it more ability to adjust for idle speed errors.

Most people that install SC's or cams have the opposite problem where when you push in the clutch when moving it dies or starts idle hunting really bad, and that's usually from the min airflow table being too low. Once they're stopped adapt idle is active and they are fine. C6's don't have a throttle cracker table in the same way C5's do.

If it's a stock car/tune it shouldn't be doing it regardless though.. If it's modded and/or had any tune changes then it's anybody's guess. Without being able to log what's going on it's going to be a guessing game

JRE-C6

So true, when the car was stock it never did this...

Jim

ffastwheels

mine is completely so k for the moment other than wheel brakes spoilers.....the engine was never touched other than regular maintenance......oh well I'll just keep digging.....

schpenxel

I'd swap out throttle body then and see what happens

Mrfitter

I also have this problem. It drives me nuts. I have ported heads ,cam ,intake ,nw102, and headers though. Clutch in coasting car idles normal. Clutch out coasting out of gear it idles at 1500. My tuner says that it's part of GMs programming and I just noticed it cause all the changes I made. I just bought an hp tuners set up and a training book so one day I can get to the bottom of this hopefully. I'd like to say thanks to schpenxel . He is a major contributor to this fourm and HP tuners fourm. I know he spends a lot of time answering tune related questions and helping fellow enthusiasts with how to articles.

schpenxel

There's a different section of min airflow table for every gear + neutral and reverse, so I suspect that's what it is on yours too. On M6's I think it only uses neutral, reverse and 1st gear but haven't messed with it in a while. He's right that GM sets them up to behave differently depending on in gear, neutral, reverse, etc., but that doesn't mean he had to leave it that way

I'm almost sure clutch in vs. out will use different sections of the table. It's been a while since I've had to mess with it, but you can log "trans current gear" to see how it's behaving and get a better idea what area to mess with

mvvette97

If the car has been tuned before I have noticed that alot of tuners change the spark table while at coast. When they bump this up it will have a high idle at coast till the car comes to a stop. With EFI live it is table B5122 and even says that table can be used to change the coast idle. Mine was custom tuned by a tuner on here and after I noticed that had a high idle like a cruise control effect while slowing down. i found that table and put it back to stock and it was back to normal

schpenxel

Yeah, more spark or more air flow can both do it. I don't mess with the coast down spark tables a ton but you're right, that can do it too

mvvette97

yea the tuner that did mine bumped that table alot for whatever reason. It was doing the high idle bad. It would hang at 1500 till I made a complete stop. I just started comparing his tune he did for me and my stock tune and just stumbled upon that table. After putting it back stock it was good. I could see where that would be useful with a very large cam possibly but is a bit overkill for a stock or small cam

Cherokee Nation

My is a auto and when driving in auto mode and I coast until I stop at a red light the idle is highter,but when I stop it goes back to normal. That is the way it should be.

schpenxel

Depends on how bad it's doing it. Yes idle RPM is set higher when moving, but not by much. 100 RPM's at most