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85k miles, intermittent issue, but more frequent all the time. In the 1500-2000 rpm range in Drive or 3rd, car shudders & rpm swings +/- 300 or so. Will not do so in 1st or 2nd gear in same or any other rpm range, so I'm thinking that it is not an engine issue. Does the converter go into lock-up in 3rd gear, or only Drive? Will knock cruise control out if set when occurs. If I drive it HARD it seems I can get it to come out of it for the most part. Any ideas?
More info: It's 98, not 97, sorry.
98 Malibu 3.1 4T40E trans, when cold the TC hunts around, cycling ever faster until after about 30 min of driving all works perfectly. Takes quite a lot of sitting in 20-30° weather for it to cool off enough to act up again. No MIL, no ODB2 codes. I've tapped into the TCC PWM SOL wire in the harness to monitor signal to TCC solenoid. Waiting to be cold enough to check while acting up, in the meantime, what am I looking for? Seems to be a modulated signal, 14V when TC out, 8V when in (I guess I expected the opposite). Do these ranges sound correct in proper operation? What do you think about tapping into the TCC REL SW to monitor it? TC kicks out fine if I ride the brake enough to activate the lights, even when it's acting up. Maybe that's the cure, ride brakes 30 min every morning!
Not sure what all goes into the TC enable allow signal, from what I read it's generally items such as throttle position, engine temp, speed sensor, maybe a vacuum sensor. I used the scanner to monitor vehicle speed, coolant temp, trans temp while it was acting up, all read steady.
Ok, to add to this, took a spin when the car was cold again, monitoring the TCC enable signal, which does fluctuate wildly when the car starts bucking as the TC goes in and out. There is no TC lock command for the 1st 10 min of driving or so, I assume due to a temperature condition not being met. So I think that I can conclude that the TCC solenoid is only doing what it is told. So the ? is, what are the inputs to the PCM that allow enable, and which of them is the culprit? It seems to be a temperature related thing, again in 30 min of driving, all is well. The engine temp is at normal in a little less time than it takes it to start bucking. Again, I monitored engine & trans temps, there is no fluctuation on the reading through the scanner. So a bad input to the PCM.... or a bad PCM? Can't see it being the TCC solenoid itself, from my understanding if those fail it's either always on or off. hmmmmm......
More info: It's 98, not 97, sorry.
98 Malibu 3.1 4T40E trans, when cold the TC hunts around, cycling ever faster until after about 30 min of driving all works perfectly. Takes quite a lot of sitting in 20-30° weather for it to cool off enough to act up again. No MIL, no ODB2 codes. I've tapped into the TCC PWM SOL wire in the harness to monitor signal to TCC solenoid. Waiting to be cold enough to check while acting up, in the meantime, what am I looking for? Seems to be a modulated signal, 14V when TC out, 8V when in (I guess I expected the opposite). Do these ranges sound correct in proper operation? What do you think about tapping into the TCC REL SW to monitor it? TC kicks out fine if I ride the brake enough to activate the lights, even when it's acting up. Maybe that's the cure, ride brakes 30 min every morning!
Not sure what all goes into the TC enable allow signal, from what I read it's generally items such as throttle position, engine temp, speed sensor, maybe a vacuum sensor. I used the scanner to monitor vehicle speed, coolant temp, trans temp while it was acting up, all read steady.Ok, to add to this, took a spin when the car was cold again, monitoring the TCC enable signal, which does fluctuate wildly when the car starts bucking as the TC goes in and out. There is no TC lock command for the 1st 10 min of driving or so, I assume due to a temperature condition not being met. So I think that I can conclude that the TCC solenoid is only doing what it is told. So the ? is, what are the inputs to the PCM that allow enable, and which of them is the culprit? It seems to be a temperature related thing, again in 30 min of driving, all is well. The engine temp is at normal in a little less time than it takes it to start bucking. Again, I monitored engine & trans temps, there is no fluctuation on the reading through the scanner. So a bad input to the PCM.... or a bad PCM? Can't see it being the TCC solenoid itself, from my understanding if those fail it's either always on or off. hmmmmm......
