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Ask Greg A Your Own Question
Greg A
Greg A, Master Troubleshooter
Category: Chevy
Satisfied Customers: 8109
Experience:  Working with Electronics & Cars for 25+ Years
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2000 chevy venture with very high idle at start up.has new ...

Customer Question

2000 chevy venture with very high idle at start up.has new iac and no vaccum leaks.
Submitted: 9 years ago.
Category: Chevy
Expert:  Greg A replied 9 years ago.

HiCustomer Thank you for asking your question on Just Answer.

Can you tell me how high is "very high"? Do you have any Check Engine light coming on?

AND

Does the idle go back to "normal" after startup?

Customer: replied 9 years ago.
Reply to Greg A's Post: vehicle will idle at 1800 rpm and higher at times.will stay at this speed until put vehicle in gear.has no engine light,no codes,readings from sensors seem ok.
Expert:  Greg A replied 9 years ago.

Wow, that is pretty high.

I would look for some other air leak around the throttle body or the Intake Manifold.

To give you some ideas, I have a procedure for testing the IAC. I know you have already changed it, but there may be some problems still in that area.

IAC Testing

This is a PDF file that you can read on your computer and print if needed.

Let me know if you have more questions.

Take Care, Greg A.

Customer: replied 9 years ago.
AIR LEAKS WERE TESTED FOR BY USE OF CARB CLEANER AND SMOKE MACHINE.NONE FOUND.IAC CIRCUIT TEST GOOD.
Expert:  Greg A replied 9 years ago.
When you say that the idle "will stay at this speed until put vehicle in gear", does the idle then go down to about 500-600 RPM?
Customer: replied 9 years ago.
NO.IDLE WILL BE AROUND 1000 RPMS AND HAVE TO STAY ON THE BRAKE TO KEEP CAR FROM TAKING OFF ON YOU.
Expert:  Greg A replied 9 years ago.

The next thing that I would look for would be a mechanical problem, somewhere around the throttle body.

I would check for binding in the throttle lines, including the cruise control.

After that, I would check the other sensors (Throttle Position, IAT, MAP, etc.) that feed the PCM and make sure they are functioning properly.

Do you have a scanner that can display what the PCM is seeing from each of the sensors?