This question relates to my 1989 TP Auto sedan with carby engine.

From a standstill and driving off sedately, it changes from first to second quite normally but is very reluctant to change up to 3rd or 4th unless I back right off the accelerator (i.e. take my foot off altogether). Once I do, it changes up smoothly enough to third and then I have to do the same again to get 4th (overdrive).

If I were to hold my foot down the engine would just rev out.

Downshifts are quite smooth and normal.

Is this only a matter of adjusting the TPS or could it be something else? Fluid level seems OK.

I've actually tried to adjust the TPS but can't undo it, even with an articulated screwdriver. Might have to take the carby off so that I can put some grunt into undoing the screws. The TPS is not the one with a single adjusting screw but the later model that is adjusted by loosening its mounting screws and rotating the TPS body.

regards,
Coldamus

Reset everything, take off the negative termanal of the battery over night (or ten mins), try turn the car on just to drain all power.

Then give it a try.

Reset everything, take off the negative termanal of the battery over night (or ten mins), try turn the car on just to drain all power.

there is nothing in the TCU to reset on a gen1. they are not learning.


Sounds like a TPS problem. probably just needs to be adjusted. Also I've found on a few carbies (including mine) that the TPS is worn and can not be adjusted correctly due to their age. in all cases i just picked another one from a wreckers and had it working. and yeah they are a cow to undo the bolts for!

Sounds like a TPS problem. probably just needs to be adjusted. Also I've found on a few carbies (including mine) that the TPS is worn and can not be adjusted correctly due to their age. in all cases i just picked another one from a wreckers and had it working. and yeah they are a cow to undo the bolts for!

I will have another go at the TPS mounting screws. These only have screw heads. On my EFI wagon, the TPS mounting screws have bolt heads as well as screwdriver slots, so you can use either a screwdriver or a socket on them. If I can get these off, I'll replace them with the bolt-head type. However I think I've fractured my finger already trying to undo them. It has swollen up to nearly twice normal size.

According to the Haynes manual, the TPS resistance between terminals 2 and 3 should be 8% of its total resistance. Total resistance of mine is 5.2K ohms so 8% would be 400 ohms. It actually measures at 1.4k ohms. When I move the throttle through its range, the TPS resistance changes smoothly so I think I'll be able to adjust it if I can undo the muddy basket!

Thanks for confirming
regards, Coldamus.

When describing the symptoms, I was wrong about the change from 1st to 2nd being normal. It is reluctant to change up from any gear.

Had another go at the TPS and finally got one screw undone. I had to use the screwdriver as a cold chisel on the side of the screw head and hit it with a hammer. Once "cracked", it was OK to adjust. I could not budge the back screw but was still able to adjust the resistance back to 680 ohms. Took three hours but made absolutely no difference. It has to be something else??

regards
Coldamus