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Why idle is staying to high, RPM's at 2000, in.

Tiny
MRSDAVENPORT
  • MEMBER
  • 2004 CHEVROLET MONTE CARLO
Why idle is staying to high, rpm's at 2000, in park, in drive with no acceleration 1500 and at 50 mph 1500-2000. Wehave checked for vac. Leaks, fuses, throt. Body cleaned. Iac and o2 sensor checked. No check engine light. What else might be the problem?
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Monday, February 4th, 2013 AT 10:42 PM

7 Replies

Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Block of the mouth of throttle-body, any effect on the idle? That should kill the engine. If no effect on idle, you definitely have false air getting in there from somewhere.

The throttle valve is closing?

I always check for codes, I don't care if the lite is on or not. I've had inactive codes point me in the right direction.
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Monday, February 4th, 2013 AT 10:58 PM
Tiny
MRSDAVENPORT
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We had it put on a computer, its not sending any codes. We changed iac, tps and used a vac. Gauge to check for leaks. We cleaned the throttle body. Tried to reset, by disconnecting the battery. Nothing we have done has helped or fixed the problem. So any further suggestions as to what is causing the problem, will be recieved with much gratitude!
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Monday, February 25th, 2013 AT 4:47 PM
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Did you try blocking off the mouth of throttle body to see if it effected idle? Humor me.
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Monday, February 25th, 2013 AT 6:29 PM
Tiny
MRSDAVENPORT
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  • 5 POSTS
We did block the throttle body, it died, right away. We dont know what else could be causing the problem. Thank you for your help.
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Wednesday, February 27th, 2013 AT 3:25 PM
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Some possibilities. Inspect.
High resistance in an iac valve control circuit.
The correct pcv valve, properly installed and proper operation of pcv valve.
Proper operation and installation of all air intake components. Check the maf sensor, where applicable.
A tampered throttle stop screw, where applicable.
Damaged throttle plate--throttle shaft--throttle linkage--cruise control.
Skewed high TP sensor/ circuit issue.
Excessive deposits in the iac passage or iac pintle.
Excessive deposts in throttle bore or on throttle plate.
Vacuum leaks.
A condition that the iac valve can not overcome.

I know you had no codes, but, there is a high idle speed code listed for your vehicle, even though the code didnt set. The above possibilities were listed for that code. I realize you have already checked some of those issues.
If you have a scanner that will show live engine data or have a friend that has a scanner that will show live engine data, now would be a good time to use it.
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Wednesday, February 27th, 2013 AT 4:41 PM
Tiny
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Thank you so much. Thanks to your list, we now have hope again, we will look into the items you listed and have it put on a computer again. I will let you know how it goes! Bless you for your help
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Wednesday, February 27th, 2013 AT 7:55 PM
Tiny
JDL
  • MECHANIC
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No problem. Let us know what you find.
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Wednesday, February 27th, 2013 AT 8:42 PM

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