RPM's fluctuating under load - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 04-03-2009, 12:04 PM   #1
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Default RPM'* fluctuating under load

Howdy,

Most prominent at highway speeds, the RPM'* in my '97 Bone SE fluctuates between 2500 and 3000 when there is a load on the car such as climbing any type of grade (although there is fluctuation at time on the flat also). I recently had the 4T60E in it gone through as it had burned up. Also recently replaced the plastic upper intake manifold and spark plugs, water pump & hoses, alternator and battery, serpentine tensioner and belt. I seem to recall fluctuation prior to the trans going out (funny story I'll tell later) but there was too much other activity going on to isolate it.

Anyone seen RPM fluctuations like this? I'm wondering if it going to get worse, and am looking at ECM as the cause. Does not fluctuate at idle, so does not appear to be idle controller.

JB
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Old 04-03-2009, 12:10 PM   #2
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My wifes van had problems with surging while in cruse. After getting a SES light for a EGR valve. I replaced that and the surging is gone.

I have noticed some surging on my 97 bonnie. I get this around 45 MPH when under heavy load in 4th gear only. If I shift out of OD it'* gone. That problem is so intermittent that I haven't tracked it down but suspect the torque converter is going in to lock up.
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Old 04-03-2009, 12:20 PM   #3
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Thanks, Dan! No Check Engine light yet, and usually, as you did, it will pop on with an EGR problem with an OBD2 car. The problem I am experiencing does seem to be electronic, but under steady throttle it would seem to be more of an electronic control problem to me, but just guessing here.
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Old 12-10-2011, 10:19 PM   #4
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I have almost the identical problem as you describe but for a 2000 PA w/ 143K miles. Has anyone got ideas?
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Old 12-11-2011, 09:51 AM   #5
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Could be a sign of a flaky crank sensor.
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