4+3 overdrive

[David c]

I am having problems with my 4+3 overdrive on my 88. The overdrive will engage just fine but will not go off when I floor the gas pedal. The car has 48,000 miles and I have changed the fluid and filter in the overdrive unit. I need help, thanks.

[larry bud]

Could be a few things... Can you disengage the OD manually? If so, the relay should be fine.

Check the Throttle Position Sensor (TPS). This is what send the signal to the ECM as to how open the throttle is. If it's reading a continuous low value, the ECM will never think you've got the pedal floored.

If this checks out to be OK, could be the ECM.

I'm betting on the TPS

[David c]

Yes I can disengage the overdrive by pushing the button. I will check the TPS and then the ECM. This car still has the original ECM, so maybe that could be the problem. Thanks for the info.