acceleration issue at 80 mph

[Denasti]

Well I have taken my ride well over 100 MPH on the trek to Dallas. If you live in Texas then you know IH35 from Austin to Dallas is a virtual race on a Friday night. Needless to say, this was a few years ago and countless repairs I have done. I have replaced the head, radiator, coil, wires, and most service items in the last 3 months.

I would like to thank all of you for the hints I have looked up and diagnosed all my problems readily and saved thousands.

But back to my new problem. I have turned this car finally over to my son and he loved it but recently on a trek to the inlaws through the hill country, I drove the car instead.

At around 80 mph I slammed the throttle down to pass a few cars on the uphill and nothing happened. No kick down or real acceleration to speak of. I tried several times on downhills also to see if perhaps it was lack of power but nothing. It seems that at 80 mph or 2900 rpm that the transmission will not downshift to get into the power band. At 75 mph it will downshift fine.

Strange becuase I recall this car being a rocket ship at 80 mph and pulling like there was no end. Any ideas? full throttle switch perhaps?

There are no codes on the stomp test and the cars runs great to this point. I also had 24 mpg average on the trip.

[tim]

The car's mileage would be helpful. Since you have done all the other stuff in the recent past, and the car is getting 24mpg, it can't be that bad.
Does this one have the kickdown switch button under the pedal when you floor it? Besides that switch, the tranny's internal kickdown shift is based on line pressure in the valve body and the lambda between that and the data from the speed sensors. You could get check/replace the speed sensor in the tranny when you drop the pan for the filter service. Finally, the tranny control may very well have programming to disallow kick down above a certain speed, but from your description of the car's prior performance, probably not the case here.

[winfred]

the tranny's in m20 cars are not computer controled they run a regular kick down cable, if the stomp test works the throttle position switch is working, it's hard to say whats the problem without getting my hands dirty

[Denasti]

Yes, it does have the switch in the floor. The car does downshift but at that speed it just won't. I may be wrong but I recall the car would down shift with the pedal depressed and when you floored it then it would down shift again? Does this sound right?

I am not sure of the last time the tranny was serviced so I will get that done soon and perhaps new fluid will help. The car has only 121k on it.

Thanks for the help in advance.

[niall]

will it downshif manually at that speed