Automatic Transmission intermittenly drops out of 4th (OD) to 3rd

[jackchoo]

This does not happen all the time but mostly I notices in the mornings, on my way to office. I'd be cruising nicely at 55mph at 4th gear (with overdrive ON) and suddenly it goes down to 3rd, as I notices the revs going up too. Sometimes it recovers back to 4th pretty quickly sometimes I need to play with the accelerator a little bit to get it back to fourth (accelerate then ease up a little).

This I notice happen a lot when I'm cruising at 50-55mph then I hit a gradual slope but also on flat roads it happens...

What could be wrong? what can I do?

[rogoman]

The TPS resistance strip most likely has a bad spot in it; this happens from normal wear and tear. To verify this, disconnect the TPS harness connector then use an ohmmeter to measure the resistance between the center pin and one of the other pins. As you turn the throttle by hand, the resistance should smoothly change.

If the TPS is bad, it's not repairable; you need to replace it.