High idle

My 2002 Impala 3.4 V6 (125,000 miles) has been doing the same thing for some time, intermittently. Sometimes if I turn off the engine, like at a stop light, and restart it, the idle returns to normal.

It may be the idle air control valve (IAC). My Haynes manual troubleshooting section says that may be a cause. Yesterday, I removed it, cleaned it, and cleaned the inside of the opening in the housing where it is installed. Both had a lot of carbon buildup. That did not help. My next step will be to replace it.

It is easy to get to, and you only need to move a few things, and have the right torx screwdriver to get it out and back in. Best of luck!

I have this same problem with my car. With no solution found. Anyone who can clue me in would be appreciated.

I just had the idle air control valve replaced, no fix.
I am starting to question the PCM, although it could be any one of the sensors feeding it.

My car idles high. Have to shut it on-off two to three times to reset it. My car also idles at sixty mph sometimes. It has gotten to the point that it appears that even when I step on the brake, the engine revs higher. It is crazy. My mechanic cannot find the problem.

Someone please help!

Car:
2002 Chevrolet Impala, 3.4L engine, Automatic.

Symptoms:
Intermittent high idle upon start.
Intermittent high idle while driving (as if the cruise control is activated).
Intermittent high idle (audible) when at stop after driving (even if the car idled fine upon start).

Findings at Shop:
None.
No diagnostic codes.
High idle blamed on IAC (idle control motor).
(It appears that when the car idle fine nothing is even sending questionable data to the PCM).
(It appears that when the car is idling high, nothing points to a specific sensor/control)

What I did:
Shotgun sensors until I found a something that seems to fix the problem.

Sensors replaced:
IAC (intake air control valve, replaced at shop for $250.00 (parts and labor).
IAT (intake air temp sensor, purchased for parts store for $15.00).
TPS (throttle position sensor, purchased at stor for $40.00).

What finally worked for me was the replacement of the TPS.
The car now seems to be working fine (hopefully it continues to do so).
It could have been linked to all three for all I know.
I did replace them in steps (first the IAC, then the IAT, then the TPS).
The only thing that proved to make a difference was the new TPS.

My suggestion to anyone that has this problem.
Replace these three items, they are cheap when purchased at a parts store (not from the dealer).
They are all in the same area on the motor/intake.
All the parts should cost you less than $150.00.
You need some tools (torx drivers, extensions, socket wrench, etc).
For a novice, within one to two hours you should be done.

Hope it works for you.
I suffered with the problem for two years. I am so glad that it finally appears to be over!

My 2001 Chevrolet Impala still has the high rev at times.
I have replaced the same parts and still the problem is here.

I have a 2003 Impala with the same problem. No diagnostic codes, just tells me the rpm's are high when in manic mode (well, duh!). I have replaced all three of those sensors (the TPS twice because I was afraid I bought a cheap one the first time), looked for vacuum leaks (found a small one and fixed that), tried driving with the cruise completely disconnected, tried adding an extra return spring to throttle. Problem persists. There must be a GM mechanic out there somewhere who has run into this? I really do not want to have to replace BMC on this car, it is just not worth the cost.

Okay, I finally seem to have corrected the problem on my car. Discovered two rubber grommets that were badly worn and have had no problem in the several weeks and 1,500 miles I have driven since replacing them.

Number one is in the middle of the PVC tube (GM part# 595), under the throttle body/accelerator cable bracket. Cannot really see it at first but easily accessed once you remove the three 10mm throttle body bracket bolts. Number two is on the back end of the Emissions Control tube (GM part # 584) that runs from the air breather tube to the back of the engine block.

The grommets are identical. Unfortunately GM will not sell them separately and I could not find anything comparable at my local parts store, so I ended up having to buy GM units. Part number one costs $17.95. Part number two costs $40.00, but since the grommets are identical and the rest of my original tubes were fine, I just bought two of the PCV tubes and used the second grommet on my original ECT. Technically should be about a seventy five cent fix if you can find grommets elsewhere, but still less than $35.00 if you are stuck buying GM and definitely worth it in terms of safety and gas savings, not to say general frustration.

Would be interested in hearing if anybody else tries this and finds it fixes their car, too.

I have a 2003 3.4L Impala with the same issue, fast idle problem. I had a tech2 connected when my Impala did the fast idle deal. The IAC showed twenty two counts standing still and went up to forty five when it should be maybe two or three counts. The TPS showed 0 ( zero)% (rotation), 0.45 volts. I am assuming 0.45 volts is okay. So something is commanding the IAC to open which would be the PCM. My fast idle did not start until after I replaced my cat and a few months before my downstream oxygen sensor. Here is what I think is happening. The IAC is being opened in response to the engine running rich or perceived as running rich. A fuel injector maybe sticking for a fraction of a second each time or all of the FI's. Or the downstream ox sensor is picking up something. I have to say though my car runs really good lots of power off the line no hesitation at any throttle position. Not getting the best gas mileage though. So I am going to try a can of Seafoam in the gas tank. Could also be the PCM itself. Could be a bad contact or wire. I had something weird happen a long time ago and I found the connectors on the PCM were loose. So I disconnected the negative then positive leads on the battery and took both connectors off the PCM and squirted with electrical contact cleaner and reattached and whatever it was went away. Unfortunately I do not have anymore time now to look into this. Will pick this up again in the spring. As bgoodwill stated I had replaced all rubber earlier on the engine including the rubber grommets for the valve cover bolts so on my car they are good.

I have a 2003 Chevrolet Impala 3.8 and have had this high idle after driving it a little bit. Could not figure out why or what the cause. I finally figured out it was the o-rings on the fuel injectors. I replaced the o-rings and the car runs good and it does not come close to over heating. I looked and read all the forums and nobody ever said the injectors. I hope that this can help some people fix the high idle and it is cheap.

Hi,

Back on March 7th I submitted a question regarding my 2001 Chevrolet Impala. At that time I informed you that my car was going into a fast idle when I was either driving it or came to a stop. To make it come to a normal idle, I have to pump the gas peddle a few times. This drops it back to a normal idle. However, as soon as I drive off, it picks up again.

Your reply stated that there was the possibility that either the throttle position sensor (TPS) or the iddle air control valve (IAC) could cause this fast idle. I decided to replace the TPS but this was not the problem. It is still doing the same thing. Before I attempt to have the IAC replaced, could something else be causing this problem that you can think of? Someone mentioned that perhaps the intake flap could not be opening up completely. What do you think?

Thanks,
Juanita

Look for vac. Leak, throttle body cleaner and clean out throttle body and idle air sensor, mit have to remove the idle air sensor and clean it ma ual.--Wrl

I have a 2001 Chevy Impala with a 3.4L. When I start the car, it will idle fine however when I go to take off with it, it wants to pick up speed and idle high (will go as fast as 45MPH without touching the gas!). When in park after it wants to go its own speed/rpm, it will still idle high. I have changed the plugs, wires, coil packs, the sensor under the packs, throt. Positioning sensor, fuel filter (fuel pressure is perfect), o2 sensors. What else can it be? I am trying to advoid the dealer, as I can not afford to pay them and they won't help me a bit! Thanks for your help!

Where would I locate the part? Thank you very much for the advice!

Car has been fixed. It was a defective Idle speed control motor. Replaced it with a new one from Auto Zone for $52.99 and problem solved! I appreciate your help you have provided us!

Rob

Why does the engine sometimes shifts on high idle when driving? If I stop and take my foot off the brake the car will idle at high speed. What is the cause?

In reply to your question as to whether the engine light has come one, the answer is no.

Any other suggestions?

Thanks for your prompt reply.