RPM's going up in neutral
 

Hello all,
My 02 z28 has 61k miles and has been complaint free until now. In the last day when i take my car out of gear my rpm's go up for a few seconds before going down. For example if I coast in neutral at 2k rpm, the car idles up to 2.5k before idling down to 1k when im at a complete stop. Any ideas?

Thanks

Got a cam or a tune in the car??

If you know its 100% bone stock, it could be a Dirty IAC valve

BUT being that I have the same issue and it is tune/drivability related, I vote for that first. This car has 36k on it and never had the hanging idle issue, and still again with a bolt on dyno tune, no issues. But the car was tuned in 30-40 degree weather when the cam went in. Soon as it hit high 70's and on into the 80/90 degree range it hangs idle like crazy and you need to come to a complete stop for it to drop down.

It will also search for idle like crazy and if not up to operating temp/closed loop it acts funny.

This car and yours probably needs a retune and a retune in the weather it will be primarily driven in.

Car has a vortech blower and tuned. This was all done 5 years ago though, and has been problem free.

Mine does the something similar occasionally. Just holds onto the revs for a bit before returning to idle after a rip on it. I just ignore it, but it most likely is the IACV or FICV. look around the intake and maybe do a little freshening up of the ports. And a little TB/Intake cleaner can be your best friend.

Check the IAC, and get the car retuned. Also scan it, any engine codes??

Also clear/reset the the PCM/DTC (Diagnostic Trouble Codes), ODBII PCM's tend to not like anyone fuckin with their settings and will make adjustments to compensate and ultimately the driveability takes a down turn. I'd try that first and see if it acts better. It could just need that!

This is all assuming the motor is good shape.

What you are describing is a tune related issue for me. :bang:

Mine does the same. Annoying as hell. Mines definitely tune related.. Not for long as I just bought HP Tuners yesterday... :)