One thing I can recommend is getting an ultraGuage, best $100 code reader you will buy, and it is a data streamer as well, and you can read what your tps sensor is seeing at that exact time, I have one and I love it. Buy one, hook it up and keep an eye on your tps that way and see if it's acting up next time the rpms jump on you.
And it may be a long shot, but try this:
The throttle body assembly is replaced
The throttle body is cleaned
The engine control module (ECM) is replaced
The idle air control valve (IAC) is replaced
Power disconnection (battery cable, ECM fuse, etc.) (Delphi ECM only)
Turn the ignition ON.
Turn the ignition OFF for 15 seconds.
Turn the ignition ON for 5 seconds.
Turn the ignition OFF for 15 seconds.
Start the engine in park/neutral.
Allow the engine to run until the engine coolant temperature is greater than 85°C (185°F).
Turn the A/C ON for 10 seconds, if equipped.
If the vehicle is equipped with an automatic transaxle, apply the parking brake. While pressing the brake pedal, place the transaxle in drive (D) for 10 seconds.
Turn the A/C OFF for 10 seconds, if equipped.
If the vehicle is equipped with an automatic transaxle, while pressing the brake pedal, place the transaxle in park/neutral.
Turn the ignition OFF. The idle learn procedure is complete.
Resurrecting this thread to see if a solution was found. I'm having the same problem. When I depress the clutch, the RPMs will jump up. Today I was in stop and go traffic, and it would consistently go to ~2000 RPMs when I would depress the clutch, or if I had the car out of gear with the clutch out. Putting the car in gear will drop the RPMs immediately, and from there they will stay in the normal range for the gear/speed.
I have an '04 manual.
That's a perfect case of a bad or very dirty Idle Air Control Motor. They're cheep and that's exactly what they do when they go bad. Vacuum Leaks also could be it, but those are usually a consistent higher than normal idle until it's fixed. The IAC is a Butterfly valve bypass port flow controller...... So when the Butterfly Valve shuts. It's a tiny valve that throttles open~shut fine tuning the tiny amount of air flow it needs to idle. If you get lucky you can take it out, clean it, it's shaft and the IAC port in the throttle Body very well. Throttle Body Cleaner is good stuff. Get around the Butteryfly Valve very well also. That's a calibrated gap and if that gap is dirty that that's one more thing the IAC has to make up for.
If you pull the Vacuum line off the Brake Booster while it's running It'll idle very high and the IAC should close. Than unplug the IAC and it should stay closed.. than plug the Brake Booster line back in and and if it idles down to normal than the IAC is bad and doesn't operate like it should or the shaft is dirty and it's gummed up and stuck open. If it idles down below normal and almost dies than the IAC shut like it should. Plug it back in and it should come up to normal idle. That's just a quicky test. But it may have intermittent issues with engine temp, It's a dirty electric part. If it was my car I'd buy a new one, clean everything in there and not bother with that 2 minute test.
Oh yeah, very important. The Aveo's air Inlet Flex Hose cracks. They all do. If it is cracked, than it's sucking air after the Air Filter! Causing a dirty Throttle Body and dirty IAC motor and unfiltered air to the engine/crankcase through the PCV. Those hoses are stupid expensive and it'll crack again. I used Black Rubber Gasket Maker on mine and my friends Aveo. I put a nice looking bead in every flex ripple and it will now outlast the car and after a few months of dust you can't tell it's not original.
Last edited by Lola; 06-07-2013 at 05:00 AM.
Thanks for the info. I'll take a look at the IAC valve (assuming THIS is what you're talking about. I replaced the intake hose last year when I replaced the head. I noticed it had a leak when I was putting everything back together. Not sure if I was running it cracked, or if it cracked when I flexed it during disassembly of the car.
One thing about the idle speed is that while the RPMs are consistent when it's revving high, it's not consistent as to when it happens. It seems to be independent of outside temp or even engine temp. Sometimes it might do it when I do a cold start, sometimes it might happen when I've been driving for an hour.
I tried the above idle learn procedure yesterday, and the car was behaving afterwards (It was running about 900 RPM on the way to work this morning), but I'm sure I might be up to 2000+ RPM on the way home today.
just one clarification on this does it do it all the time or only some of the time? as one possiblity is (kinda hard to explain where it is but will try my best) there is a little clip that olds the throtle cable in place just to the right of the throtle body on the front this may be sticking caused by perhaps a freaying cable inside it happened to my mothers lanos was a case of taking the throtle cable off the body pulling back the protective sheefing and checking for any damage.
Only some of the time. Yesterday, for instance, when I left work it would idle at 2000 RPMs. I went to the store and when I started back up, it would idle at ~900 RPMs for the rest of the way home.Originally Posted by marmite369
Since we're all guessing here, I'll take a swag. Intermittent MAP sensor glitch affecting ecm load calculation. Any codes stored or engine light?
HTHY-- the krusty mechanic.
And of course it could also be a vacuum leak like Lola and the others said, The IAC is really a controlled vacuum leak. I was trying to provide a fresh perspective.
No light. My scanner cord is MIA. Need to find it and hook it up to the PC.
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