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fix the vacuum leak
Most likely, the alternator is going out. It puts out more at higher RPM's, so it would charge more going down the road than it would at idle. Good Luck!!!
what is the down side of the 1997 buick park avenue
there is an Allen screw and a nut on the throttle cable you loosen the nut and the screw and adjust it to make it idle up or down.
A vacuum leak can cause that.
how do you adjust the idle on a 2002 toyota van
you can adjust it via the idle control valve.
the RPM should idle 700 - 900
clean or replace your idle air control valve.
The racing up and down at idle is call enging loping, usually caused by a vacuum leak. It could also be caused by a sticking choke at the carb. Whatever the case may be, you will need to start by hooking up a smoke machine to find the source of the leak. Also check your coolant level. my 1991 Toyota 4x4 22re had the same race up and down idle. it was a low coolant level.
The idle is preset at factory. No adjustment provisions are provided. In cooler temperatures, it will take a little longer for the idle to come down. If the vehicle continues to have a higher than normal idle, then you will need to take it to a shop where they can diagnose the problem. Driving around with a higher than normal idle can damage the transmission.
I have found that replacing the PCV valve AND chasing down any exhaust manifold leaks usually does the trick.