Why would RPMs fluctuate at constant crusing speed??

Old Mar 13, 2010 | 06:56 PM
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Why would RPMs fluctuate at constant crusing speed??

So if im crusing flat highway @ 50-55mph my RPMs will be at ~2200; suddenly they'll drop to 2000 then back to 2200 then back to 2000. this may go on for miles.

replaced and cleaned the Mass airflow sensor,
What else could be going on here?
Otherwise, when accelerating its fine
97 f150 4x4 4.2L

thx
Frank
 
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Old Mar 13, 2010 | 07:31 PM
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Is it manual or automatic?!
 
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Old Mar 13, 2010 | 07:31 PM
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If you have an automatic transmission, it's normal.
 
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Old Mar 13, 2010 | 07:32 PM
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Torque converter?
 
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Old Mar 13, 2010 | 08:43 PM
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have you checked your eyes?
 
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Old Mar 14, 2010 | 01:45 AM
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Torque converter locking and unlocking.
 
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Old Mar 14, 2010 | 10:31 AM
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it an automatic. Thats normal?? Really??
seems odd..
 
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Old Mar 14, 2010 | 11:48 AM
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i aint' buyin' it either...

Originally Posted by franki21
it an automatic. Thats normal?? Really??
seems odd..
sounds like the answer you get from a shifty dealership...
 
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Old Mar 14, 2010 | 12:04 PM
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Well, those are the symptoms of the TC locking and unlocking. Whether it's normal or not can be debatable, it *IS* normal to some degree. Try driving it with the OD off at those speeds, what does it do?
 
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