I had this weird problem start the day before yesterday. I was driving and everything was normal until i stopped at a red light. When i stopped i noticed my engine was revving at right around 3K and was not falling. I have an 08 6MT, so I had the clutch in, and the revs did not move when i put it in neutral and let the clutch out either. Very very slowly the revs started dropping to normal idle RPM. So i got to the next light and pretty much the same thing happened. Basically all the way to work it was the same thing.

Yesterday i did not have this issue at all, or at least that i noticed.

Today on my way to work it was very bad, but i started to watch exactly what was happening with the RPMs. When i would approach a stop, i push my clutch in and get the car out of gear and into neutral and brake until i stop. Lets just say when I clutched in i was at 2400 RPM. The car would actually climb (again, my foot is not on the gas) to around 3K fairly quick, and sometimes up to 3200. It would stay there for a while, and then depending on how long i was stopped, it might very slowly start dropping (when i say slow, i mean... i have the southbend flywheel, so I'm used to fairly quick raises and drops).

Sooo... I was racking my brain as to what this could be... Here's what i was thinking, and i have not had time to check ANY of these items, but i wanted to see if anyone has experienced this.

Throttle Bodies need cleaning (i cleaned them fairly recently, but wouldnt mind doing it again)... The only thing with this is that the RPMs were CLIMBING, and i wasnt sure if they would do that if this was the issue.

Cold... I'm in NJ and its been fairly cold here, so i dont know if this might cause it

I just read on here that maybe the A/C has something to do with it, but it seemed to only be on the ATs, not 6MT

The mat... I didnt check to see if the mat was pinched in the pedal or on top of the pedal, but I'm assuming its probablly not that... if it is... I'll never post again LOL.

Any help would be appreciated. Thanks.

 

If it was bouncing I'd say idle control valve...I have had that issue before. With this though, not sure. It could be a sensor malfunction I guess, throttle is reading 0% (or whatever it is at idle) but is actually stuck open at 20% (or whatever). Check sensors and go from there. I wish I could be more help but I am new to this car so don't know how it all acts yet.

 

Its just strange because it doesnt happen all the time.

 

I had this issue and I cleaned out the throttle bodies. It only got worse. I've heard cleaning them worked for others though.

 

What upgrades do you have?

 

I've got k&n typhoon CAI, and Berks HFC.

I actually cleaned my air filters a little after this, and they didnt seem that dirty, but I have not had this issue since, so maybe that helped.

The strangest part when this was happening was that the revs were climbing with my foot off the gas. It just didnt make sense to me. Even if it was the throttle bodies, they would only get stuck, not keep opening... or so I'm assuming... I dont know. Like it said. I havent had the issue for awhile. This was also when it was cold out, I it seems to me that our cars HATE the cold and do some goofy stuff.

 

Off topic post:
Couldn't help to notice that you had PSIU in your name. Are you a brother in Psi Upsilon?

 

When the intake or plenum is not connected or bolted down correctly air can seep through and cause an unwanted air/fuel ratio which causes higher rpms.

 

SURE AM!!! You too? what chapter?

 

But would this cause the revs to actually CLIMB without my foot on the gas?

 

ive been having the same problem for years. mine is an 08' auto though.

it actually revs high and lunges forward. that's with my foot on the brake. it happens when its super hot out. or when my ac is blowing hard and its hot.

kinda scary and embarrassing. I have to shut the car off at a light sometimes to reset it.

any help would be great.

 

Sounds like you fixed it...

 

It's the cold. When the engine's still cold, this happens quite often. If you also notice, when you pull away from a cold start in 1st gear and left off the gas w/o putting it into neutral, the revs will hang at around the same RPM that you revved it to.


Happens to me all the time, and I'm in SoCal... aka no cold weather, just cold engine.

 

any update on this issue? i may have the same problem.

 

Search for a vacuum leak anywhere along the intake tract. This technically includes everything up to and just past the primary O2's, but it is most likely something under the hood.

If nothing obvious is discovered, try spraying carburetor cleaner all along the area (but not by the filters themselves if open rather than sealed in airbox).

While spraying, if the idle changes, you've found your leak.