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1986 Mercury Grand Marquis Sedan Base

1986 Mercury Grand Marquis Sedan
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May 19, 2012, 1:43 pm

Bob A

Question: rpm surge at random

The car has about 170 thousand miles, and is in good mechanical condition. Recently began the following: At idle, rpm will increase of its own volition, and if in gear would lunge forward if the foot brake had not been applied. the duration of the surge varies. punching the accelerator has no effect. Happens at random, but becoming more frequent. I've heard there is an ignition part subject to heat damage with age, but can find no hints on the web. Thanks for any suggestions.

May 23, 2012, 9:51 pm

Richard W
Expert Mechanic

The ignition will not cause your problem. You need to check your Idle air control valve. And also make sure you don't have any vacuum leaks.

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