The car has an automatic overdrive transaxle. I purchased the car back in 2010 with 59,000 miles on it. I had a reputable transmission shop put the tranny on a machine and flush it, along with fluid & filter change. About 8 months after I had the car, I started noticing where the transmission seems to slip in and out of overdrive at speeds above 40MPH. But I never notice it when the cruise control is turned on. When I disconnected the lockup solenoid, the problem wasn't there. But the check engine light kept flashing. And I was told not to run the car with that solenoid disconnected, and plugged it back in. After I plugged the solenoid back in, the check engine light never came back on again. One place told me to replace the solenoid. Another one told me to change the Throttle Position Sensor. As of today, I have 70,000 miles on the car. And it still has that minor problem. Other than that, the car is in excellent shape otherwise.
I have a question which might pertain to the lockup converter solenoid. on 1992 Oldsmobile Cutlass Ciera
seek diag and est from trans shop