Question about 2000 GMC Jimmy

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Bucking at speeds over 60 or after it has rained

The garage wants to replace the air pump and i think it has somthing to do with the tune up I just did. Maybe the bosch spark plugs could be the problem. Not only does it buck after a few bucks at 65 it will downshift into a passing gear and wont shift back up until i slow to 50 or 55 for a few minutes. What should i do ?

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If you can find a place will be scan your system for you that would be good. Where ever you take it, have them look at the O2 sensors switching. You may have an O2 sensor being really lazy or not working at all. I don't think your air pump has anything to do with your problem. You may be experiencing a torque convertor lock up problem as well. Definitely get a data stream done before changing any parts that you don't need replaced.

Posted on Nov 01, 2008

  • Lee Quiroz
    Lee Quiroz Nov 01, 2008

    One thing I failed to see, check the distributor cap for moisture in it especially after it rains. I didn't see the "after it has rained" comment. the convertor most likely has nothing to do with what is happening. I don't thing your O2 sensors have anything to do with it either now. Double check the timing on your truck instead.


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what mileage on that engine, from last tuneup.? and total miles
100k,? what?
if that is engine buck and not transmissions slip or unexpected shifts.
then that is called MISFIRE<
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