2001 Chevrolet Cavalier Idling/running Too High

Thomas2270 · 2022-04-17T13:44:48+00:00

I start the car and it jumps up to 2,000 RPMs, it also is affecting it when it’s in gear. I can put it into gear and not hit the throttle and the car will slowly accelerate. I currently have no codes being thrown and I have had a computer hooked up and ran all sorts of tests (the only way I could lower the idle was by manually changing the idle speed on the computer). I have checked good for vacuum leaks, replaced MAP sensor, cleaned IAC valve, checked Throttle Control Sensor, checked all fuses, and more. Does anybody have an answer or advice?

JACOBANDNICKOLAS

✓Experienced Mechanic
110,240 POSTS

Hi,

This vehicle has a throttle cable. Are you certain it isn't frayed and causing the throttle body not to return to the closed position?

Do me a favor. Disconnect the throttle cable at the throttle body and see if the RPMs go to normal.

Let me know.

Joe

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Apr 17, 2022 at 2:42 PM

THOMAS2270

MEMBER
9 POSTS

I will run that test, I do believe the throttle body does return to the close position but it’s worth a shot.

Apr 17, 2022 at 8:56 PM

THOMAS2270

MEMBER
9 POSTS

I disconnected the throttle cable and there was little to no change. I’ve had some people suggest looking at the ambient air sensor and the cam sensors so I’m going to check those out next. Anymore suggestions or advice?

Apr 18, 2022 at 6:07 AM

JACOBANDNICKOLAS

✓Experienced Mechanic
110,240 POSTS

Since the IAC has been replaced without change, I need to know if you checked where it mounted to make sure there was no carbon or dirt that could prevent it from moving properly.

Also, I have attached testing procedures for the IAC circuit. Take a look through them and let me know if they help.

Let me know.

Joe

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Apr 18, 2022 at 1:41 PM

THOMAS2270

MEMBER
9 POSTS

I did check and cleaned where the IAC was mounted, also did a sea foam cleaning which gets sprayed directly into the throttle body so it’s pretty clean, but I will go through those procedures and see if that has an effect.

Apr 18, 2022 at 10:24 PM

JACOBANDNICKOLAS

✓Experienced Mechanic
110,240 POSTS

Hi,

Let me know what you find when going through the diagnostics I attached above. Also, if you have a live data scan tool, let me know what the short-term fuel trims are.

I'll watch for your reply.

Joe

Apr 19, 2022 at 10:12 AM

THOMAS2270

MEMBER
9 POSTS

I don’t have the proper tools to run all those tests, but I was messing with the IAC (manually changing how far it came out) and I did get it to lower to about 1,300 RPMs. And then when I started it up again it shot back up above 2,000. So, I’m going to replace that today and run some tests on the computer and see if that will fix it.

Apr 20, 2022 at 12:20 AM

THOMAS2270

MEMBER
9 POSTS

I replaced the IAC and there was no change, I can manually pull the valve out and install the valve, and it will run just above where it’s supposed to be. But when I start it up again it will shoot up to 2,000, I can manually adjust it and not plug the valve in and it will run fine.

Apr 20, 2022 at 3:20 AM

THOMAS2270

MEMBER
9 POSTS

I feel dumb, but I do have a vacuum leak coming from my intake, I’m guessing it’s the gasket so when I get that torn apart I’ll let y’all know if that is it for sure.

Apr 20, 2022 at 6:22 AM

JACOBANDNICKOLAS

✓Experienced Mechanic
110,240 POSTS

Hi,

It sounds like you found the problem, and please don't feel dumb. That is a really easy thing to miss. Remember, this is a plastic intake so be careful.

I attached the directions for removal and replacement. The directions include torque specs as well.

Let me know if this takes care of the issue.

Take care,

Joe

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Apr 20, 2022 at 1:19 PM

THOMAS2270

MEMBER
9 POSTS

I replaced the intake gasket, and it did lower the idle, it now averages about 1,100 RPMs. The idle does surge and fluctuates, it will go as low as 900-1,000 and as high as 1,400- 1,500. I was wondering if y’all had any ideas on how to fix that, I found no vacuum leaks. It is throwing an EVAP code but I’m not sure if it would cause that. The car is definitely drivable, I just want to get it to 100%.

Apr 30, 2022 at 11:24 PM

JACOBANDNICKOLAS

✓Experienced Mechanic
110,240 POSTS

Hi,

If there is a leak in the EVAP, it can possibly cause an engine vacuum leak. What code is it? Also, let me know what has been done so far to eliminate the EVAP code.

Take care,

Joe

May 1, 2022 at 11:42 AM

THOMAS2270

MEMBER
9 POSTS

P0440… and I haven’t done anything yet, I was told i would need a smoke test to properly diagnose what needs fixed, I figured I would ask before I just started replacing stuff.

May 2, 2022 at 1:53 PM

JACOBANDNICKOLAS

✓Experienced Mechanic
110,240 POSTS

Hi,

The code indicates the EVAP is unable to achieve or maintain a vacuum during the diagnostic test. So certainly, there is a leak that is likely causing the idle issues.

A smoke test is what I would do first. If there is a leak, it will show smoke where it is located.

I attached the diagnostics below specific to the code. Take a look through them and let me know if you are comfortable performing them.

Take care,

Joe

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May 3, 2022 at 8:49 AM

Idling/running too high