Any car buffs out there that can help?

[blahblah99]

I have an automatic 87 Supra non-turbo that likes to switch from first gear to third gear at around 10mph. If I floor the gas pedal at standstill, the car goes up to 10 mph (2500 rpm max) and likes to change gears to 2nd, then immediately to third. It does this everytime, whether I put the pedal to the metal, or if I accelerate slowly. I do have an ECT button but that does not seem to do anything.

I've checked the throttle valve cable for appropriate length and replaced transmission fluid. What is wrong? 🙁

 

[IGBT]

Throttle position sensor??

 

[blahblah99]

I'll check on that tommorow.. doesn't that adjust the idle speed?

 

[IGBT]

There's a feedback loop to the computer that the trans.may see. I don't know about your car but I've seen that mentioned in other forums as a common failure. It's a small mechanical device on the throttle body.

 

[Brutuskend]

Although this usually happens with standard Trans., broken motor mounts can cause this kind of thing to happen....

 

[JC]

Does that trans use a vacuum modulator? A bad modulator/vacuum leak could cause the trans to not see the load the engine is under, resulting in early shifting up.

JC

 

[Thegonagle]

I don't know how this transmission works, but if it has a kick down cable, that's where I would start.

It's not likely to be bad engine mounts causing this problem.

If the engine is running fine, it's not likely to be the throttle position sensor (TPS).<-- Didn't you get the memo? 😉

 

[blahblah99]

Alrite, I checked the throttle position sensor and it looks like its working good... I hooked it up to a meter and turned the sensor manually and it gave out proper resistances.


What about this vacuum modulator thing and where would it be located at?

 

[JC]

Well on most American transmissions it's hanging off the trans case just above the rear of the trans pan. Has a single vacuum line to it, for manifold vacuum.