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Dave Nova
Dave Nova, Buick Technician
Category: Buick
Satisfied Customers: 19451
Experience:  ASE Master Certification. GM World Class Certification
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Buick LeSabre: 1997 buick lesabre 3.8 fast idle when it s

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1997 buick lesabre 3.8 fast idle when it starts
Hello and thank you for using JustAnswer. My name is XXXXX XXXXX I will do my best to help you with your Buick problem.

Is the check engine light on with engine running?
Customer: replied 5 years ago.
NO
The problem is most likely in the idle air control valve (IAC) on the throttle body. You could try removing the IAC and cleaning it with carburetor cleaner spary to see if this makes a difference, if it does not help then replace the IAC.

#4 is the IAC

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Customer: replied 5 years ago.
I CHANGED iac NEW ONE STILL IDLES AT 2500RPM'S
Is the check engine light on with the engine running?
Customer: replied 5 years ago.
NO
Will the idle speed eventually drop on its own if you let the engine idle, or do you always have to turn the engine off and restart?
Customer: replied 5 years ago.
TURN KEY OFF AFTER 5MIN'S
A high idle can also be caused by a vacuum leak. With the engine running, spray carburetor cleaner all around the perimiter of the intake manifold. If the engine idle changes at any point, you have found a vacuum leak. Also with the engine running, remove the oil fill cap and see if there is excessive suction there. This would indicate a vacuum leak from the intake manifold gaskets internally into the crankcase.
Dave Nova and 4 other Buick Specialists are ready to help you
Customer: replied 5 years ago.
WELL I JUST PUT A NEW INTAKE & GASKET STILL HAVE FAST IDLE 2500RPM'S
Is PCV valve okay? Check or replace the PCV valve and see if this helps. The PCV valve inside the upper manifold must have an o-ring seal in place.
Customer: replied 5 years ago.
THE INTAKE CAME WITH A NEW ONE
Customer: replied 5 years ago.
PLEASE DON'T GIVE UP
Sorry for the delay. The website was down yesterday. Make sure the O-ring is in place on the PCV valve. Beyond that you will need to connect a scan tool and monitor the IAC counts commanded by the computer vs. the actual IAC position to see if they match up.