Has anyone else had this wacky problem?

[Polaroo]

I have a 1996 Jeep Grand Cherokee, which I love, but it started doing the weirdest thing. It only happens when I have my A/C on, the speedometer will intermitently go wild, 30, to 140 to 55 to 0 back and forth, even if I am stopped and then it will also cause a hesitation in acceleration, bascially only when starting to move after being stopped, like at a stop light for example. It has even turned off on me once, when I pressed harder on the gas pedal instead of backing off for a second. It doesn't happen when the A/C is off. I have had the cables and wires checked, distributor cleaned, done a computer diagnostic which showed only that I had a faulty speedometer sensor or something so I had that changed as they figured that was the problem and it was shorting out something else..... but nope, it still is happening. I have it at the shop now and they are trying to work their magic but any info I could provide them would be a big help..... Thanks

[digitalyuppie]

I just got home from work today and then went to start my car and it wouldnt start.None of the lights work and the gages are going crazy. I dont know if that is the same problem or what. The gages are moving even when the car is off.

[Polaroo]

Sounds worse than mine but along the same lines. Is this the fist time anything like this has happened? The only thing moving like crazy on mine is my speedometer. One of the mechanics I took it to says it sounds like something in the wiring.... crossed wires maybe or sensor problems..... sending conflicting signals to the computer system..... I'm pursuing this further next week..... I'll keep you posted!

[Bob D.]

digitalyuppie, problem sounds like a weak battery or bad connection at the battery terminals - I've heard about those symptoms many times and its usually one of the above.
The flagging gauges are the giveaway.
If the battery checks good, clean the battery connectors.

Polaroos symptoms sound a little more complicated, but I would still check the battery and batt. connectors.

[Jroot1969]

I have a similar problem. Mine does it but sometimes it does work, sometimes it flutters, and sometimes it just stays in one spot like 30 MPH the odometer on instrument cluster does not work when it does this but the one on the VIC does work. I have replaced the speed sensor and no change, unplugged the speed sensor and no change! If anyone knows what else I could try I am game, thanks for reading.

[rhandwor]

Originally Posted by Polaroo

I have a 1996 Jeep Grand Cherokee, which I love, but it started doing the weirdest thing. It only happens when I have my A/C on, the speedometer will intermitently go wild, 30, to 140 to 55 to 0 back and forth, even if I am stopped and then it will also cause a hesitation in acceleration, bascially only when starting to move after being stopped, like at a stop light for example. It has even turned off on me once, when I pressed harder on the gas pedal instead of backing off for a second. It doesn't happen when the A/C is off. I have had the cables and wires checked, distributor cleaned, done a computer diagnostic which showed only that I had a faulty speedometer sensor or something so I had that changed as they figured that was the problem and it was shorting out something else..... but nope, it still is happening. I have it at the shop now and they are trying to work their magic but any info I could provide them would be a big help..... Thanks

Especially If you do any mud running I would thoroughly check the wires from the speed sensor which I think is located on the transmission tail shaft. At least check 3 or 4 foot back.

[wpatters1229]

I have a 93 and it was doing some weird things with fast idle when starting and then would not start sometimes or other weird things so I starting thinking that all of this is controlled by the PCM (computer) but not as a failure but bad connections. I first cleaned and checked all the body ground connections. Same problems. I then pulled off the big multi-connections that go into the PCM....wow some of the contacts had green corrosion on them. I have an electrical connections cleaning kid for computers and used the spray on the connections. I then plugged the connector in and out about 6 times and then sprayed the contacts again. Left them wet and plugged it back in and bolted it down.
ALL the weird problems stopped!!

[StumpedGMowner1]

Sounds like corroded pcm connection or faulty ground wires. I agree with wpatter1229 check pcm connection.