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Q: idle control

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I have a 1975 c-10 chevy pickup with an ls1 engine and every time i put it in drive or revers it revs up specially when it's cold

My car has 50000 miles.
My car has an automatic transmission.

A: My sense is that it is sucking in air throu...

My sense is that it is sucking in air through a broken vacuum hose. If it sounds like when you put it in gear and the engine lays over on the motor mounts, it is opening up a source of vacuum leak. The extra air speeds up the idle. Try to get someone else to put it in gear (keeping their foot hard on the brake!) while you do a visual inspection under the hood. Look for excessive engine movement on its mounts (to check for worn motor mounts) and look and listen for a vacuum leak. If you are still having trouble, have a certified technician come to your car’s location to diagnose the revving problem you are experiencing.

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