High idle

AXLE · 04-24-2010, 09:38 AM

My '01 sometimes idles too high. This can be anywhere from 1250 RPM in nuetral to up to 2800 RPM. The throttle is not stuck. There is no stored code, the SES is not on, and I have removed and cleaned the IAC and the throttlebody. If I shut it off, then re-start it the problem resolves itself and the idle returns to about 700 RPM as read on the dash tach. Sometimes I need to restart it two or three times to get the idle back down, it idles lower each time I re-start it.
Is there something else I should be looking at, or a way to diagnose this problem?

JLw7123 · 04-24-2010, 09:43 AM

is it when u start it up or when you drive for a while and stop at a stop sign.

Vella's Alero · 04-24-2010, 01:38 PM

throttle position sensor?

AXLE · 04-25-2010, 10:41 AM

Quote:

Originally Posted by JLw7123

is it when u start it up or when you drive for a while and stop at a stop sign.

After driving for a while and it's fully warmed up.

zzyzzx · 04-26-2010, 09:52 AM

How many miles are on the car?

AXLE · 04-27-2010, 12:59 PM

Just turned 58K

zzyzzx · 04-29-2010, 10:05 AM

At 58K the IAC should be good and not even dirty. I suspect that you have unmetered air or maybe a vacuum leak.

Mori01 · 04-29-2010, 02:23 PM

I'm going to go with vacuum leak..

cherrington17 · 04-29-2010, 02:50 PM

just take the tach needle off, and put it back to where it should be.

comanche · 04-29-2010, 07:16 PM

Possibly false air. Common problem on these is that the UIM leaks a little.
It would be good to see live data numbers.

AXLE · 04-30-2010, 11:21 AM

I replaced the manifold gaskets shortly after I got it, at about 52K.
I find it hard to believe it's a vacuum leak/unmetered air unless you consider the fact that a stuck open IAC is unmetered air. It's idles and runs fine, but after about 15 to 20 minutes on the highway I can notice the car will no longer slow down much when I let off the gas. If there is traffic I'll shut the motor off when I come to a stop because I'm fighting it with the brake pedal, and it's about 1500 RPM in nuetral. Re-start it and usually there is no change, so I do it again and the idle comes down to 700 RPM.

A vacuum leak would be pretty much a problem 100% of the time and I just can't see how it could be effected by me simply re-starting the motor. I just now replaced the IAC and if the problem persists I'll check for a vacuum leak.
Thanks for the suggestions.
Oh, and what the hell is "live data numbers"?

AXLE · 04-30-2010, 11:24 AM

Quote:

Originally Posted by cherrington17

just take the tach needle off, and put it back to where it should be.

Thanks for nothing.

zzyzzx · 04-30-2010, 12:24 PM

Quote:

Originally Posted by AXLE

A vacuum leak would be pretty much a problem 100% of the time and I just can't see how it could be effected by me simply re-starting the motor.

Vacuum leaks can be intermittent! You can have something leak only after the engine warms up and something expands. Another thing people forget is that devices that use vacuum can leak too, it's not always a hose or fitting.

Havign said that, at 52K miles, I'm having trouble understanding why you would have any type of vacuum leak or bad IAC. I don't trust IAC's past 150K, but yours is no where near that!

AXLE · 04-30-2010, 12:29 PM

Quote:

Originally Posted by zzyzzx

Vacuum leaks can be intermittent! You can have something leak only after the engine warms up and something expands. Another thing people forget is that devices that use vacuum can leak too, it's not always a hose or fitting.

Havign said that, at 52K miles, I'm having trouble understanding why you would have any type of vacuum leak or bad IAC. I don't trust IAC's past 150K, but yours is no where near that!

But the engine is warmed up. I'll see what the IAC does.

AXLE · 06-12-2010, 09:08 AM

Dug up this old thread to update it. It threw a code one night on the way home, P0122, low input voltage. The next day when I got to work & the idle was too high I unplugged the TPS and the idle immediately dropped to normal. When I returned home, the idle was again high, but not as much. Next day I removed the TPS to see if anything obvious was wrong and check the resistance. I couldn't find anything wrong so I re-installed it. Next time I drove the car it idled just fine cold & hot.
The problem has not returned in weeks, so I'm gonna have to chalk it up to a poor or corroded connection at the plug, even though I checked for that and couldn't see anything wrong. Must have been all the times I unplugged the connector that it scraped off some corrosion.