Questions and Answers

Caravan Torque Converter Q. Hi Vince, I have a 1989 Dodge Caravan with a 3.0 engine, an A-413 3-speed transaxle, 120,000 miles, multiport fuel injection, no ABS, P/S, A/C, cruise with rack and pinion steering. My problem is when I am driving at highway speed on level ground the engine rpm is at 2,100 RPM then with no acceleration on my part it will jump to 2,400 RPM for a few seconds and then go back to 2,100.

This cycle continues at irregular intervals from 5 to 45 seconds apart. If I floor the gas pedal there seems to be no slipping of the transaxle. When it is occurring if I pull the shift lever into second the RPM jumps to 4,300 RPM so it is not downshifting into second. I was wondering if it is a problem with the torque converter lockup solenoid.

I would like an explanation of how lockup is suppose to work and how to tell if it is a problem with solenoid or the torque converter. The factory shop manual I have does not go into any detail on this subject.

Thanks in advance,
Gregg

A. There are two possibilities for this problem, the Throttle Position Sensor (most likely) and the Torque Converter Clutch Solenoid.

The TCC solenoid is controlled by the PCM. The PCM applies and removes the ground from this solenoid to engage or disengage the lock-up torque converter. The lock-up torque converter is only locked up when the transmission is in direct drive and when the throttle position is not fluctuating. If the PCM receives a signal from the TPS that an increase or decrease in throttle is needed (when the transmission gear selector is in direct drive), the PCM will disengage the part throttle solenoid causing the lock-up torque converter to be disengaged.

It is common for the TPS to develop a "dead" spot in it and cause the symptoms you describe.