TPS Sensor and Auto Trans

[btwilson86]

I've had a CEL for the Throttle Position Sensor for quite some time now, and I have finally checked the resistance values. After discovering that the readings are WAYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY off from what the TSRM says they should be, I attempted to recalibrate the sensor to no avail, and decided to remove it for further inspection. The rotating piece inside of the sensor housing does not move, and after destroying the sensor in order to see how it works, I found out that it should have been rotating with the throttle linkage (makes sense).

So I'm getting a used one from the junkyard tomorrow, but I have a question.

How important is this sensor to determining when the Auto transmission shifts? Ever since I have begun work on my 87 N/A Auto Supra, I've had sporadic shifting, and I believe that this may be the cause.

Anyone have any input on this subject?

[Pretaco]

Out of all the sensors in your car, the tps is the one input that the transmission uses. Or the most important one. Is there a cable that runs from the throttle body back down to the trans? If so, thats what tells the trans when to shift down during accel, but if not, then the trans computer relies on the tps.
You should notice a big difference with a good tps.

[btwilson86]

Ok, cuz the TPS I got from the junkyard works perfectly. It's well within the resistance specs per TSRM, and this one has some metal on it so maybe it'll resist melting. I have to wait until Saturday to put it on and calibrate it, and I'm hoping I'll finally be done with this transmission nightmare.

[btwilson86]

Alright, I installed the TPS Sensor. It's well within the appropriate resistance values for all of the readings except for the infinite resistance at .7mm gap. it has to go to about .9mm before I read infinite resistance.

The TPS install has solved my rough shifting issues, but my auto trans still slips alot when attempting to accelerate from a dead stop in drive. If I put it down into "L", it locks up no problem.

I also noticed that when I'm driving at WOT, it shifts early for the 2-3 shift and the 3-OD shift. However, it's dead on for the 1-2 shift. Trans fluid is at the proper level, and the rebuilt tranny has only about 50 miles on it. Also, the cable between the trans and throttle linkage has been replaced fairly recently.

Anyone have any ideas?

[Pretaco]

Who rebuilt your tranny?

That type of slipping is usually an internal problem with on of the clutches. I would take it back to the tranny shop and get them to fix it under warranty.

[btwilson86]

Yeah, when the tranny was rebuilt the car wasn't running yet, and I didn't know much about finding a good place to work on my car. So I pulled the tranny myself and took it to a local tranny shop. They rebuilt it for 800, and put in a new torque converter for like 200-250, somewhere in there. Problem is, when I put the tranny back on the car and went for a test run to see if it worked, my engine threw a rod. So car sat for a couple of years until I got the new engine in. So I'm pretty sure it's out of warranty since it's been so long (if I ever got one). But definitely worth checking out. And I'm gonna have to go and check the fluid again to make sure that I put the correct amount in. If I recall correctly, after reinstalling the drain pan (and gasket), I had the car off when I put in the fluid, and I could only put in a couple of quarts. Not sure exactly how much it takes, but I don't think I ever checked the fluid level correctly (car at temp and idling). The only thing is I don't think it would be the fluid level if it does lock up while in "L" as opposed to Drive.... Doesn't matter, I'll check anyway.