Hi all, My 2003 SS started idling fast a week ago, Friday while driving home it was idling at 3000rpm, I figured out that if i unplugged the MAP sensor it idled fine so I pulled into a part store and replaced it, idled fine right away but only for 1 day now it idles about 1500 when starting, after its warm I hit the throttle and it drops to 800rpm but then when I start driving its at 1200rpm in gear then briefly goes to 1500 when put in neutral then back down to 800-1000rpm.

So far I replaced the MAP & Air Intake Temp sensor as well as cleaning out the air cleaner, Replacing the Idle Control Vale next "yeah! I was going to do that first but it idled fine after disconnecting the MAP", when I looked up the codes it showed an EVAP code

I have also had a problem with the throttle sticking shut after sitting for a while, I dont think this is related but any suggestions on what to clean the throttle body and intake with?

 

Is the SES light on? Any codes in the computer? When the car is cold, it will idle at about 1500 rpm until it warms up. Then the idle will drop down to about 700-800 rpm in park. With an idle that is surging , i would be looking for a vacuum leak. Use a can of carb cleaner and spray around the vacuum lines, and the edges of the intakes. If the idle makes a noticeable change, then you have a vacuum leak in either a line or gasket.

 

Light was on, code was for the evap., replaced gas cap and no more codes, as for the warm up idle its about 3000rpm now that its colder out, even hit the rev limiter at start up!! idles about 1500-2000rpm in gear "about 50 mph" then down to 1000-1200 when out of gear no matter how warm the car is.

Ive used Ether to look for vacuum leaks and found none "in dash maybe?" and would it idle fine when unplugging the MAP Sensor if it was a vacuum leak?
.........Ok, I just went to fiddle with it a little and realized the idle jumps briefly when going to the defrost setting, could that be from vacuum leak or just from the temporary loss of vacuum from moving the damper "valve- flapper what ever it is"? I also sprayed around the intake as I had a plugged up cat a few months back that caused severe backfires and found nothing there, also it is idling fine atm "800rpm".

Thanx for the reply and any future help seawolf18.

 

My 2003 monte ss had high idle and rpm surges at 2-3k while driving. Temp guage would also dance around, and fans would kick in and out crazy. I thought it was a vacuum leak or my iacontrol, or tpsensor but that didn't help. Come to find out it was the computer was bad. Had it replaced and rebooted, all the problems i mentioned went away. Total cost was 975.00. Computer gm 686.00 labor 180.00

 

Old thread for anyone reading

 

I would check the "IDLE POSITION SENSOR". IPS.. Located in the front of the engine and Maf... If you want I'll post a picture of where it's at.. Mine stuck open one time and it had went to around 3000 rpms until I cleaned it out and reset it.. Helped out big time, haven't had an issue since then... Mjclemm...

 

I've replaced the IPS along with EVERYTHING on the top-end Including the upper intake and upper/lower intake gaskets, yet this problem persists, Ive brought it to a mechanic and the local collage automotive class, neither could successfully diagnose it, I believe its a melted wire from the overheating when the cat was plugged, my wife only works 1/2mile from the house so the 12mpg its getting is fine with me, I'm sure as hell not replacing any of the wiring.

Its a damn shame because for 10 years old and 175k miles it is like new in&out,very minor rust on the radiator support and where the sub-frame bolts to the body. I'm planning to buy the wife a big suv this winter then either enter this car in the rollover contest at the speedway in the spring or parking it in the field for target practice with the .50cal

 

Or sell it cheap to me !...lol...... Damn 12 mpg, wow.. When you replaced the IPS, did you set it far enough in to start with ? It only goes in steps every time the car starts from what I read... When mine was idling real high, I pulled the IPS and it was clogged up, some cleaned it up but forget the exact position it was in.. I pulled it 3-4 times and spun it little by little IN until it idled just right, then the engine PCM corrected it from there.... Just an idea... Good luck ... Mjc..