Adjusting the GM TPS (Throttle Positioning Sensor)
by Chad Golen

In this article we will discuss how to properly adjust the GM TPS (Throttle Positioning Sensor).

If you are installing one of our 383 cubic inch engines it will require more air to start and idle properly therefore you will need to move the throttle blades to allow more airflow but once you do this the TPS voltage reading will be off. The computer needs to see the proper voltage reading in order to know where the throttle blades are at any given time to keep the engine running properly. Follow the steps below to properly adjust your TPS and keep your engine starting and idling perfectly.

In order to make the adjustment you will need the following tools:
A voltmeter, small file and a torx screwdriver will help make short work of this task.

Step #1    It will be easiest to take the throttle body off the intake so you can make the blade adjustment via a small set screw in the side of the throttle body. (see picture A)
                                                                                               Picture A
Start by turning the set screw until you see the throttle blades open slightly, (see picture B).
                                                                                                     Picture B

Step #2   You will need to remove the TPS and carefully file the holes so you can make an adjustment (see picture C) pay close attention to where you will need to file in relation to where the screws go into the throttle body, it is a rotation adjustment. You can also use a drill bit or any other tool that works to make the mounting holes bigger.
                                                                                                 Picture C

Step #3    Bolt the TPS back onto the throttle body and tighten the screws slightly so you can make easy adjustments, then take the lead on the voltmeter and pierce the center wire it should be blue in color, (see picture D) until you get a voltage reading.
                                                                                               Picture D

You will need to have the ignition key in the on position but the engine not running.  The voltage reading you are looking for is .67 volts if you have a LT1 from 94-97 MAF (Mass Air Flow) (see picture E) and .50 volts if you have a TPI from 85-92 or a LT1 1993 speed density.

                                            Picture E

Once you find the perfect adjustment tighten the TPS screws and recheck the voltage reading to make sure that it hasn't moved. At this point reinstall the throttle body, you will in most cases need to go back and forth with the throttle blade position and chase it with the proper TPS voltage adjustment until you find the spot where the engine starts and idles perfectly.
(consult Golen Tech Support for the proper idle RPM for your engine).

If you have any problems with making this adjustment please contact
Golen Engine Tech Support to avoid damage to your new engine.