94 chevy 3500 with 6.5l turbo and 4l80e trans. trans was rebuilt about 400 miles ago and new torque converter installed. fluid has good color and no burnt smell. shift normal in all gears. no engine codes. now here is the problem, it wont hold back while in O/D or drive. it will hold back while manually placed in 1st or 2nd. when driving along normally, when i let off the throttle, the rpm's fall to idle and when i give it fuel again, the rpm's will go up a little before it re-engages. ideas?

 

Here little info that may help you out

Harsh transmission shifts and no up shifts into Overdrive can be caused by a defective Throttle position sensor.
This sensor helps determine engine load.
Throttle position sensor low DTC 22

P.S This is especially true with the earlier model vehicles era 1991-1992-1993

Troubleshoot the sensor by verifying the voltage from the computer being 5.0 volts at PIN A. If you do not have close to 5 volts and within 4.8 to 5.2 volts then troubleshoot the delivering circuit. Pin A going back to the computer.
Move the wiring and harness a bit while checking pin A.

You will need to verify the throttle resistance within the throttle position sensor. If the resistance is intermittent or there is a bad connection then you can suffer shifting problems. Remember that a DTC will not always show up. The fault can still happen and not throw a DTC.


Find the pin with resisted (feedback to the computer lead footed voltage
Back probe the two wires and verify Pin C and B. One is ground and one is resisted voltage from the throttle. This is the business end of the Throttle position sensor.
To find the pins:
C should be ground. Set the multimeter on continuity and check for pin C and chassis ground. A beep will tell you that one of the wires came across is ground.
Back probe the other resisted pin going back to the computer. Actuate the throttle a bit will let you know. Also the resisted pin has much less voltage.
Actuate the throttle and you will see the resistance move in the multimeter. If it doesn’t then that pin supplies 5 volts. Leave it alone.
1. The middle pin is the one you are after.
2. Ground is what you are after.
Record the Ohms between the two while the throttle is in idle.
Once you locate and know the function of these three pins lets begin.
Go to the middle pin the resisted voltage pin. Go to Pin C and with the ignition on and truck not started check the voltage with the throttle in idle.

At idle you should get .47 to .5 volts from the middle pin or resisted pin.
Actuate the throttle slowly. There should be a dedicated and dependable rise in voltage. On some there is one break while actuating to full throttle. When you get to full throttle there should be <<<<4.7>>>> to <<<4.8>>> volts registering through the resisted pin.

Verify through Ohms the same test. You should see resistance move as well.
If the graduated range is not smooth then get another TPS.
Clear the codes by disconnecting the batteries. Reconnect and drive the vehicle.

P.S. Remember this pin tells the computer where your foot is on the fuel pedal.
It helps determine engine load. The Engine RPM (ESS) Sensor helps out as well.

 

thanks.