1996 Oldsmobile Ciera • 6 cylinder FWD Automatic • 235,000 miles

I have a 1996 Oldsmobile Cutlass Ciera with a 3.1SFI motor, I am haveing a problem at speeds between 35-40. It seems like it will not shift. This problem has developed after the 1 year warranty on the new transmission has run out. I have replaced a fuel injector that was missfiring, plugs and wires, coils, and Ignition modul but It is still giving me the problem. Any thing that I may have missed. What ever it is it is not tripping the Check Engin Light. Thanks for any info.
April 16, 2011.

Try scanning the computer for code/s-Possible causes here coule be one of the following below

Oxygen sensor.
Catalytic converter.
Fuel injectors dirty/sticking.
Mass airflow sensor/Airflow meter.
Throttle position sensor.
Crankshaft position sensor
Knock sensor
Manifold absolute pressure sensor.
EGR Valve
Fuel pressure regulator leaking or defective fuel pump.
Fuel contamination.
Foul/defective spark plugs.
Open spark plug wires.
Ignition coil/Coil packs defective.
Incorrect ignition timing.
Cap and rotor.

Note: If it doesn't apply disregard it and keep testing.

Apr 16, 2011.