Help requested: 2000 Jeep GRC rpms fluctuate at highway speed

[vonbraun]

My 2000 Jeep Grand Cherokee will cruise nicely at 70mph but will sporadically rev up an extra 150 rpms for a second or two. This results in a slightly perceptable surge forward. It happens whether the cruise control is on or not, at different speeds (although less noticable), with the A/C on or not, and whether the OD is on/off.

It appears to happen more frequently with slight resistance such as a gradual long up hill, a strong headwind, etc, but it isn't perfectly matched to these conditions either.

There is also an idle condition that may be related. After a highway trip the idle will surge between 650 and 1500 rpms on its own.

Any ideas to put me in the right direction would certainly be appreciated.

[Dale Aeppli]

Originally Posted by vonbraun

My 2000 Jeep Grand Cherokee will cruise nicely at 70mph but will sporadically rev up an extra 150 rpms for a second or two. This results in a slightly perceptable surge forward. It happens whether the cruise control is on or not, at different speeds (although less noticable), with the A/C on or not, and whether the OD is on/off.

It appears to happen more frequently with slight resistance such as a gradual long up hill, a strong headwind, etc, but it isn't perfectly matched to these conditions either.

There is also an idle condition that may be related. After a highway trip the idle will surge between 650 and 1500 rpms on its own.

Any ideas to put me in the right direction would certainly be appreciated.

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[mcs219]

Had a 1990 Caravan that did the same thing. A simple idle adjustment was all the dealer had to do.