01 SS monte Carlo

[jimran13]

Need some help people my 01 Monte Carlo at or around 50 to 65 starts to go up and down,the motor that is you can see it on the tach.needle jumps But soon as you gas it the motor stops doing all that and runs fine .My wife feels it more then me drives that speed, I am a red light to red light driver 0 to 100 so I miss it alot of times ..any ideas ,fuel filter ,injectors,trans problem ,converter,,,,I just dont know HELP PLEASE I am getting close to that 120,000 mile mark for the converter to changed Thanks JIM

[curtis73]

Its probably just a mismatch of components and programming. GMs have doen that for YEARS. What happens is it senses a little more load and downshifts (or unlocks the torque converter). Then since it shifts it senses less load and shifts back up.

Its called shift hunting and its been a problem of GMs for years. I had an S10 blazer once that when you used cruise on an uphill stretch it would start in OD, but lug down so far that when it did downshift it went all the way to 2nd. Then it powered itself up to the cruise set speed, backed off the throttle and shifted back to OD. Then 5 seconds later it would do it all over again. The easy solution was to manually shift it into D, but then you're thinking to yourself... why can't it figure that out on its own? Its just that where GM designed the thresholds for shifts causes a problem.

Next time it does that, shift it down to D and see if the problem remains. Given that GM programs their computers to have such close tolerances for shift points its probably always going to happen at some speed, it just so happens that yours is 55-60.

Another thing it could be is a faulty torque converter that doesn't want to stay locked. To test that you can tap into the TCC lockup wire from the computer with a digital multimeter; not analog. If its doing what you describe with constant voltage, then the TC is failing to stay locked. In that case the fix is a new TC. If its hunting around and you see the wire supply voltage, then no voltage, then its working as-designed but frustrating. In that case you might be able to at least change it with something like a Hypertech programer. If you alter your shifts using something like a Hypertech it might fix it, but remember its just different. It might not fix it, so consider borrowing one first before you spend your money.

[jimran13]

A friend of mine works at car max and I was telling him so he has this 4,000 computer he is going to hook up and drive to see whats going on ,,but one of his work mates says something what you said he worked for gm for a few years and thinks the same but we will see and thanks a lot Jim