Hello all~ I have a 2005 Monte Carlo LS with 198,000 miles on it. Original motor, new transmission. She drives like a CHAMP! Except, after gets up to 30-70 miles per hour, at a constant speed (not during excelleration), even with the cruise contol on, the RPM's constantly (pretty constant) jump from 500-2500 RPM's. I have taken her to Auto Zone and put on the tester. Since there is not any lights on, Auto Zone could not diagnosis it. Any idea's???

 

Sounds like the torque converter is locking and unlocking on you.

 

Os this cured by changing the converter solinoid?

 

Maf maybe be dirty..