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Engine Surging

 
Old 03-11-2011, 04:28 PM
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Golden Gael
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Default Engine Surging

Engine Revs surge between 650 and 1100 while in neutral or when at a stop. Have replaced a number of sensors and the ECU. Did 3 vacuum tests and checked the EGR valve. There are no codes except for the computor seeking the proper rev info. Anyone have any ideas??
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Old 03-11-2011, 04:35 PM
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oldalaskaman
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my vote was gonna be for the EGR, may be somethig that uses vacume, like the cruise control servo, an 02 sensor that is doin g something called 'hunting'. if you give the year of your car others will step in faster cause its probably happened to them
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Old 03-11-2011, 06:23 PM
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Tommy T-Bone
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Could be electical like a battery going south or failing alternator. Worth checking.
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Old 03-12-2011, 07:49 AM
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TWISTERUP
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Sounds like a vacuum leak.
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Old 03-12-2011, 08:20 AM
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Chuck Tribolet
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My '87 did that. It was a broken vacuum line sorta
under the driver's side headlight. Get somebody with
young ears to have a listen. That's what found my
problem.
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Old 03-12-2011, 09:37 AM
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steverichmond
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Sounds like me, Can't hear it thunder anymore. lol
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Old 03-12-2011, 09:40 AM
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Sounds like the IAC to me. Same thing happen on my Grand Prix SE, changed the IAC and it was fixed. BTW buy it at pep boys for about 30 bucks, others charge up to 200.
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Old 03-12-2011, 11:26 AM
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socalman
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Originally Posted by kimmer View Post
Sounds like the IAC to me. Same thing happen on my Grand Prix SE, changed the IAC and it was fixed. BTW buy it at pep boys for about 30 bucks, others charge up to 200.
That was my problem, only just the plug to the IAC. Check the plug first, unplug it, clean it, try it again.

Also found out the Temp Sensor can be reading temp correctly, but not signalling the ECM correctly. Fuel is constantly trying to adjust due to faulty temp reading to the ECM.

A scanner told me this, but no code because it wasn't completely malfunctioning.
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Old 03-12-2011, 01:29 PM
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Chuck Tribolet
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Originally Posted by socalman View Post
That was my problem, only just the plug to the IAC. Check the plug first, unplug it, clean it, try it again.

Also found out the Temp Sensor can be reading temp correctly, but not signalling the ECM correctly. Fuel is constantly trying to adjust due to faulty temp reading to the ECM.

A scanner told me this, but no code because it wasn't completely malfunctioning.
On my '87, the FSM shows two coolant temperature
sensors. One feeds the gauge on the instrument
panel, the other feeds the ECM, which makes emission
decisions based on the info, and triggers the low
temp fan (with dual fans the high temp fan has a
third on/off sensor).

My '01 Nissan Pathfinder is the same way (except
no two-fan option).
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