Friends,

I'm trying to research this but can't find the words. Just recently when moderately accelerating (sorta heavy) around 70mph my RPMs started to jump around. It's like the car doesn't know which gear to shift into. Once I let off the gas it was fine.

Then today when accelerating moderately (medium not heavy) around 35mph the RPMs jumped around some again. Once I coasted back to a normal accel it was ok.

Other than that, everything shifts fine and runs smoothly for 208,000 miles.

What do you think? Flush the fluid, change the filter, TPS Sensor? Thanks!

 

Are you saying that the engine RPM is actually fluctuating or are you saying the it's the RPM indication fluctuating?

 

THAT is a damn good question. I think it's the indication fluctuating, because the transmission doesn't feel jumpy or hesitating or anything like that. But then again it could be and so gradual that I don't feel it. I'll pay attention to that next time.

 

Sounds like the TPS going out.

 

You said it was jumping. I guess you need to describe it better.


If it's indication it could be the Tachometer in the instrument cluster.

 

Update 2. I was able to take it out for another highway run today to get some detail back to you guys and it's definitely the transmission rpms jumping not just the tachometer.

Details: Cruising around town 35-45 no problem, then I hit the gas hard at the onramp and took her to 65 no problem, then when I cut back on the pedal to hit cruising speeds the rpms started jumping from 2k to 3k to 1.5k, and the transmission was jerky, it was like it didn't know what gear to settle into. Hit the gas for a moderate acceleration it downshifted no problem, but then again trying to hold that cruising speed it happened again. Off ramped back to 35-45 speeds and it was driving just fine.

WTF? TPS sensor? Old fluid, bad filter? Hopefully not a transmission going out? Thanks fellas.

 

It could be a dead sport in the TPS variable resistor...around the spot where the throttle plate would be during cruise.


Do check the trans fluid. See if it smells burnt or is black. Let some drip on to a white rag or paper towel and eyeball and sniff it.


When's the last time you changed fluid in the trans?

 

Here's some tests of the TPS. It's intended to be performed using a digital Voltmeter, which is hard to pick up a dead spot in the resistor so an Ohmmeter is usually used for this.


You can use an analog Voltmeter if you keep a sharp eye out for an interruption in the voltage reading when slowly moving the throttle from idle to wide open throttle. I've managed to see it myself.


Do the tests at Pin 2.


Use a small safety pin to back probe at pin 2 wire.


During the tests the ignition switch must be to RUN, but engine not running.





Safety pin:





Example of back probing:

 

Thank you CCKEN.

So a bad TPS then eh? I have not changed out the fluid or the filter since I've owned it and I'm not sure when it was last done! I did drain some out and add some as I was going to do a gradual flush but I never got around to finishing it.