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I recently noticed that when coasting or breaking is followed by acceleration (seems to be only when the car is moving between 25 and 40 mph) that there is a slight jerk. After recreating the problem a few times I noticed that the rpms jump up to just a little over 2000 then after the jerk it drops back to 1000-1500 which is usually normal. While it hasn't happened every time these conditions are replicated, it has been fairly constant. Hoping that it would be an easy fix, I just had the transmission fluid flushed. The car is at a little over 100k miles. Transmission is automatic. Any thoughts on what the trouble might be?

Observations that I haven't been able to confirm yet: It seems like the problem occurs less going uphill (haven't tried recreating the problem going down hill); It also seems like the longer periods of driving (15+ minutes) result in less occurrences though I'm not certain of this either yet.

UPDATE: I have noticed that when I take my foot off the gas between 25-35 miles per hour the RPMs drop down to just over 500. At any other speed it remains over 1000. If I begin accelerating before the RPMs drop below 1000 at the speeds where I'm having this issue it doesn't seem to jerk but if I let it drop below 1000 it does. Does this change the circumstances at all?

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Is it worse when the engine is cold? –  Nick Jul 29 '12 at 12:26
    
by cold do you mean when the car has sat for a long time (say over night) or do you mean physically cold? If you mean sat for a long time not running then possibly yes... I haven't been able to confirm that yet though this is something I've considered. If you meant physically cold I have no way of knowing that right now because it just started a couple of weeks ago and we've had warm weather the entire time. –  Kenneth Jul 29 '12 at 13:20
    
yes, when the car has cooled of completely to ambient temperatures. –  Nick Jul 29 '12 at 15:01
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Is there a check engine light on by chance? Also, out of curiosity where was the "transmission flush" performed and what was included in the flush? –  cinelli Mar 22 '13 at 17:23
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@EricFossum converter lockout clutch would be felt at coasting speeds as well as slight uphill acceleration... –  cinelli Mar 22 '13 at 17:25
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