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1993 Deville Engine surging at idle?

2222 Views 3 Replies 2 Participants Last post by  Ranger

I have a 1993 Deville. The engine surges very fast at idle when the engine gets hot. I already replaced the Throttle pos sensor because of E27, E55 and E85. The errors are gone but the engine still revs very high at idle sometimes. If I put the car in nuetral and tap the gas the idle drops back down to normal. Does this sound like the idle speed control valve is sticking? How can I test it? What else can cause the engine to rev up very high at idle?

Thanks in advance,
1 - 4 of 4 Posts
A vacuum leak will cause a high idle, but since you can lower it by tapping the gas pedal I would suspect the Idle Speed Control (ISC) motor. Does it ratchet and click when you shut it down?

I have seen it clicking and jumping when I shut the car down at times. Looks like it is trying to go to a home position. Does this mean the motor is bad?
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