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Erratic Idle


Guest ShlbyTurbo

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Guest ShlbyTurbo
My 1990 turbo laser doesn't like to idle at a steady rpm. usually revs high when i press the clutch for about 20 or so seconds, then drops to normal. Also has erratic idle upon start-up. any ideas?
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Guest 614Streets
ShlbyTurbo you most likely have a vacuum leak. The idle problem will be more pronounced on colder days as you probably know. The reason it gets better after it warms up is simply due to expansion. On higher milage engines weak valve springs , worn valve seats , cracked rubber lines , and leaky intake gaskets, as well as cylinder pressures that vary from cylinder to cylinder contribute to idle charecteristics. Brake Boosters commonly leak after 10 years as well.
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Originally posted by ShlbyTurbo:

My 1990 turbo laser doesn't like to idle at a steady rpm. usually revs high when i press the clutch for about 20 or so seconds, then drops to normal. Also has erratic idle upon start-up. any ideas?

sounds like your base idle set screw has come loose and backed out a bit. There is a big hole in the throttle body with a screw inside of it that controls idle speed. I would adjust this screw (with the car running) and see if that helps. Sometimes the screw can back itself all the way out of the hole (thanks to boost) and be missing, so if you see the hole, but there's no screw, you need a BISS (base idle set screw).

 

Another thing (hope its not, they're expensive) it could be the IACV (idle air control valve) stuck open.

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