Shifting problems?

[roush028]

i own a 2000 Grand Prix GT- 3800 Series II. while im driving around if im going up a hill or step into the gas a little bit and try to get it to go a little faster or if im going up a hill and im trying to keep my speed up, the car shutters pretty bad and jerks almost like it doesnt want to shift. it will eventually shift down after a few seconds of doing this and go. but if you just step into it hard and make it kick dow it will and go just fine. but just easing on the gas to keep speed up a hill it likes to jerk and hestitate first. any ideas of what it could be? its pretty annoying. its almost as if it doesnt want to shift down when you need to pick up speed unless you stomp the gas really hard.

[grandprixgtx00]

most likely a bad throttle position sensor. does it throw an SES light?? the throttle position sensor tells the kickdown cable when to make the tranny downshift. its like a $10.00 part, and pretty easy to change. you can also try cleaning it before you replace it...

[roush028]

thanks! i greatly appreciate it. do you happen to know how to get to it and how to replace it? and no it doesnt throw a SES light.

[grandprixgtx00]

well uhh...lets see. first your going to have to take the plastic motor cover off, the TPS is located on the throttle body. it will look like a little black round thingy...haha, trying to explain it here.

there will be 2 little bolts holding it in there, im pretty sure they are torque bits though. i would take pics, but my camera is broken i believe if you are standing on the driverside of the car, and looking at the throttle body, it will be located on the right side of the throttle body,I'm pretty sure, but dont quote me on it...its been a while since i changed on there is also of course a harness connected to is with some wires. the harness is fairly small though.

if this doesnt help you much, i will attempt to find a camera that works, and take some pics for you...

[grandprixgtx00]

another thing to think about...how long has it been since the car has had a tune-up/fuel filter??? it also may be a plugged fuel filter.

[tblake]

Originally Posted by grandprixgtx00

most likely a bad throttle position sensor. does it throw an SES light?? the throttle position sensor tells the kickdown cable when to make the tranny downshift. its like a $10.00 part, and pretty easy to change. you can also try cleaning it before you replace it...

I will agree that The TPS is a likle cause for this problem, but he has a 4t65e tranny and there is no kickdown cable. The PCM uses the TPS signal along with other sensors to determine the appropriate gear range.

As you stated the TPS is very easy to change, however its quite a bit more expensive than $10.00. Even the cheapo ones are about 40.00. At least they are where I live.

[BNaylor]

Originally Posted by grandprixgtx00

most likely a bad throttle position sensor. does it throw an SES light?? the throttle position sensor tells the kickdown cable when to make the tranny downshift. its like a $10.00 part, and pretty easy to change. you can also try cleaning it before you replace it...

There is no separate kickdown cable to make the tranny downshift. The TPS provides a d.c. voltage output to the PCM module to let it know throttle position angle. It ranges from .4 volts at idle to around 4.5 volts at WOT. The PCM module provides a 5 volt reference signal to the TPS input. All automatic shifting and downshifting is controlled by the PCM module via shift solenoids depending on where the transmission range switch (PRND321) is set. Other sensors used for shifting are the VSS and input turbine sensor. TPS input and output voltages should be checked along with linearity while moving the accelerator before attempting any removal.

We have a thread with pics at our Tips & Maintenance forum which shows sensor locations such as the TPS. See Link below.

Click here

Although it doesn't hurt to check it the TPS very seldom if ever cause or cures "fishbite" or "chuggle" problems which is the TCC locking and unlocking when it should not. GM has a TSB out on the issue but it is B.S. and a waste of money since it recommends replacing the TPS for this problem and the sole cause. It can be caused by a tranny issue or secondary ignition problem such as spark plugs, ignition wires and coil packs.

The OP should post the mileage and the last time the tranny was serviced such as ATF and screen filter. Also, a scan with a trans capable scanner may help. Even though there may be no SES/CEL light some TCC related codes or others like pressure control may be stored for retrieval. Also, when were the spark plugs and ignition wires last replaced?

[grandprixgtx00]

yes, my bad...4T65E's do not have a kickdown cable. haha