[A.j. Schreiber]

is it possible for a bad TPS sensor to cause this?

 

[ImperialCrown]

I wouldn't expect the fluid and filter change to fix this, so don't sell it to them as a possible repair, only as a maintenance. Getting into the TCM diagnostics would be very important as a start. If you can't get a hold of a scan tool to read the TCM, I would farm the job out to someone who can.
A TCM code might possibly show up in the odometer display during an instrument cluster self-test (hold reset button in. then roll the key on, then release the button and write down any codes that may appear).
Some early minivans would hang in 3rd after a downshift with the cruise control on because of a wiring change issue. I don't believe that 1998 was affected.
A good generic OBD II scan tool should be able to watch the TPS with this happening.

 

[Doug D]

I would think if there is any TCM fault codes stored that a code reader would at least show a P0700 generic transmission code in the PCM. P0700 basically tells you the transmission has a problem and you need the TCM checked for fault codes.

 

[A.j. Schreiber]

We do have a high end OBD2 scanner, I will look over it thoroughly. As far as I know there is no check engine light illuminated. I was thinking the same thing with the fluid change IC, not a fix, but probably require maintenence, he did mention that it wont shift back to 4th until he stops and shuts the car completely off. Once he starts it up again everything is AOK until he needs to kickdown again

 

[chuzz]

Could the problem be related to the solenoid pack on the transmission? Maybe a loose or corroded connection?

 

[A.j. Schreiber]

Possible, but since it can shift from 3-4 and 4-3 in flat everyday driving I dont think that that's it

 

[NssJ]

Something physically sticks at the throttle where pedal cable connects to kick down cable? Only gets stuck when activated quickly, won't catch with normal shifts, but something catches and stays with kick down. ...

 

[A.j. Schreiber]

thats what I'm thinking, havent had the chance to test a few theories myself. If this customer comes back in and we find a fix I'll let you know. Just wanted to share this cause I've never heard of a 41TE doing that before and to pass it along to someone else maybe

 

[ImperialCrown]

No kickdown cable on a 41TE, it's all electronic. You need to see what the TCM is seeing.

 

[A.j. Schreiber]

I hope this customer comes in again this weekend. And I am aware of that fact IC, but maybe at or close too WOT the TPS is getting stuck or the throttle body is doing something funky. This is my therory mainly because it's apparently only related to big throttle inputs.

 

[ImperialCrown]

The mechanical slotted throttle shaft return for the TPS is a fairly positive arrangement. Mechanical binding and staying at a high throttle signal is unlikely. You can watch TPS voltage on a scan tool while slowly opening and closing the throttle. It should climb and fall smoothly with throttle opening and closing.
I did see this once before and the problem turned out to be a harness rub-through where it gets cut by being routed against the transaxle pan and other sharp corners/bolt heads of the transaxle. Then salt water got in and turned the copper wire strands into a green paste. Had to splice, shrink wrap and tie the harness back to fix it. I believe that they were yellow and yellow/stripe wires to the TCM. I'm not saying that it is what is going on here, but it may be something that you want to look at.

 

[A.j. Schreiber]

Unfortuneatly this customer never returned, as always I appreciate your input everyone. I really wish he did come back, I wanted to solve and fix this one