weird idle when sitting and wont rev done when not in gear when slowing down

[1997eclipse rs]

okay so here is the problem i let my car warm up everyday before work but it always revs up by itself when its just sitting there i know that cant be normal so it could be idling at at 1,000 then all the sudden to 2500 then all the sudden to about 700 then back up?....

also when im driving when im pulling up to a stop light and when i put it in netrual and just roll up to it my car stays reving between 1000 and 2300 hundred my vw never did that and it was normal is this common with the dsm's or is their something wrong

thanks in advance for the answers

 

[xcasbonx]

also when im driving when im pulling up to a stop light and when i put it in netrual and just roll up to it my car stays reving between 1000 and 2300 hundred

This is a common nuisance on the 420a that some people have. The RPM's will "hang" for awhile when going to neutral and rolling up to stops. It will hang for awhile, then usually level off.

Sounds like an issue with your IAC (idle air control) valve. You should pull the throttle body, remove the sensor and make sure it is physically in working order still. Clean all the buildup out of it and anywhere on the TB as well. Put a new TB gasket on or use RTV (TB gaskets are about 2.99 at the parts store). Reinstall everything, check for any vacuum links and see where you stand.

 

[1997eclipse rs]

thanks ill try that tommorow and see if it helps!

 

[slickers111]

This is referred to as the DSM Auto Rev Feature.
Its kinda funny at times. My N/T loved to do it, and my TSi did it for a little while when i first got it.

Its the IAC.

 

[1997eclipse rs]

oh i hate it because i leave really late at night and we have speed bumps so everytime i go to netural or slow down my car stays reved up and then mmy neighbors hate me haha