Throttle Position Sensor (TPS) Adjustment
Now that you’ve installed the TPS following the directions posted elsewhere on the site, it’s time to adjust the TPS for optimal performance using either WinALDL software or a Digital Voltage Meter as shown below.
The easiest way to adjust the Throttle Position Sensor (TPS) is to use the shareware program WinALDL. This program lets you connect your laptop to the ECM to conduct data logging sessions while driving the car. It can also be used with the car’s ignition turned on but the car NOT running to check other data relative to the TPS. Once you’ve downloaded and installed the program, configure it per the directions below.
When you first open WinALDL, this screen will appear. Select the configuration button. You may see a Com Port error message. If you do, the next step will address in the error message.
Check the tag on your ECM for its service number & then scroll through the ECM Type field until you find that service number. The green arrow points to the COM Port for your laptop. If you’ve selected the correct COM Port, you’ll see data scrolling when the key is in the on position and when the engine is running. Hit the Exit button on the configuration box.
There are two ways to adjust the TPS:
Percentage & Voltage Method using WinALDL
Voltage Method using a Voltage Multi-Meter (VOM).
NOTE: The percentage & voltage adjustments are completely intertwined i.e. when you get the percentage number within parameter, you’ll also have the voltage within parameter and vice versa. The two numbers are dependent on each other so if you fix one, you’ve also fixed the other one.
NOTE: If you get a “Check Engine” light error indicating that a TPS failure, it is most likely caused by not having the TPS driver nut in the correct position.
Adjusting the TPS using WinALDL
With your laptop connected to the ECM Data Plug, open the WinALDL program and turn the car ignition to the “on” position but DO NOT START THE CAR. Select the “Dash” button which will open the Dash Display (Yellow Arrow). Then select the “Sensor Data” button which will also show the TPS Throttle Percent position (yellow block/red arrow). This is done with accelerator in the idle position i.e. keep your foot off of the pedal 🙂 You want the TPS reading in both the Dash & Sensor Display to be as close to zero as possible (-0.3 in this example). The green arrow is pointing to the voltage reading which should be close to 0.50 volts. As noted above, when you have the percentage number correct, the voltage number will also be correct.
Now press the accelerator pedal all the way to the floor and hold it there until the Dash Display stabilizes with the Wide Open Throttle (WOT) percentage reading. Anything over 80% is acceptable and in this example it’s 92.9% as you can see in both the Dash and Sensor Data display. Again, percentage and voltage are co-dependant and at WOT the red arrow points to the TPS voltage reading which should read 4.2 or more. In this case it’s showing 4.31 Volts.
Here’s this same car with the engine running and idling at 900 RPM. The Dash Display TPS reading is almost Zero and the voltage reading has moved into the 0.50 volt range.
Adjustment is made by rotating the TPS driver slightly clockwise to increase (counter clockwise to decrease) percentage & voltage. You need to back off the driver set screw 1/2 of a turn to set them properly. As noted above, Do not over tighten the driver nut. Once the driver is properly positioned, tighten the Allen screw to lock it in place. If you get a “Check Engine” light error indicating that a TPS failure, it is most likely caused by not having the TPS driver nut in the correct position.
NOTE: Whenever you adjust your carb idle via the idle adjustment screws, you need to check the TPS settings.
Voltage method with a Digital VOM
This method is used mostly by the “hardcore” technician. In this case we’ll be taking voltage readings directly from the connector at the TPS using a Digital Voltage Meter. You will need a couple of paper clips or pieces of thin solid wire to reach into the back of the TPS connector when it’s plugged into the harness. This will allow you attach the leads of your Volt Meter to the various pins for testing. There are three pins in the connector, 5V, Ground, and Sensor. DC voltage is measured between pins Sensor (+) and Ground (-). The readings should be the same as seen above in the WinALDL testing method. A voltage check across the sensor (harness plugged in, key on) should show approximately 0.5VDC at idle and 4.2VDC or more at full throttle. Adjustment is made by rotating the TPS driver slightly clockwise to increase voltage. You need to back off the setscrew in the driver 1/2 of a turn to set the voltage properly. Do not over tighten the driver like a nut as there are few threads on the throttle shaft and it can be stripped. Once the driver is properly positioned, tighten the Allen screw to lock it in place.