What Does the Throttle Position Sensor Do?

The Rochester Quadrajet Throttle Position Sensor (TPS) plays a crucial role in the engine management system of a vehicle. Here's what it does:

Monitors Throttle Position: The primary function of the TPS is to monitor the position of the throttle in an internal combustion engine. It is typically located on the butterfly spindle/shaft of the carburetor, in this case, the Rochester Quadrajet, which is a popular model used in many vehicles.
Sends Data to the Engine Control Unit (ECU): The sensor sends data regarding the position of the throttle to the Engine Control Unit (ECU). This data is critical as it influences how much fuel and air should be mixed for optimal combustion.
Adjusts Air-Fuel Mixture: Based on the information from the TPS, the ECU adjusts the air-fuel mixture. When the throttle is open wider, more air enters the engine, and the ECU responds by adding more fuel for a balanced mixture. This is essential for the engine to perform efficiently under different load conditions.
Improves Engine Performance: By ensuring the correct air-fuel mixture, the TPS helps in maintaining optimal engine performance. This includes smoother acceleration, better fuel efficiency, and overall improved vehicle responsiveness.
Helps in Idle Stability: The TPS also plays a role in maintaining a stable idle. It informs the ECU about the closed position of the throttle, allowing the ECU to adjust the fuel mixture and idle speed accordingly.
Detects Throttle Opening and Closing Speeds: The sensor can detect how quickly the throttle is opened or closed, which can influence the responsiveness of the engine and the smoothness of the acceleration.

How to Adjust the Throttle Position Sensor on the Car?

NOTICE: The plug covering the TPS adjustment screw (Fig. 24) is used to provide a tamper-resistant design and retain the factory setting during vehicle operation. DO NOT REMOVE the plug unless, in diagnosis, the "System Performance Check" indicates the TPS Sensor is not adjusted correctly or it is necessary to replace the air horn assembly, float bowl, TPS sensor, or TPS adjustment screw. This is a critical adjustment that must be performed accurately and carefully to ensure proper vehicle performance and control of exhaust emissions.

If necessary to adjust the TPS sensor:

a. Using a No. 48 (.076") drill bit, drill hole in aluminum plug covering TPS adjustment screw (Figure 25), drilling only enough to start self-tapping screw (approximate drilling depth 1/6" to 1/8" ). NOTICE: Use care in drilling to prevent damage to adjustment screw head.

b. Start a No. 8 X 1/2" long self-tapping screw in drilled hole in plug, turning screw in only enough to ensure good thread engagement in hole.

c. Placing a wide-blade section of screwdriver between screw head and air horn casting, pry· against screw head to remove plug. DISCARD PLUG.

d. Using Tool BT-7967A or equivalent, remove screw (Figure 26). '

e. Counect digital voltmeter (such as BT-2815) from TPS connector center terminal (B) to bottom terminal (C). (Jumpers for access can be made using terminals 12014836 and 12014837. Make jumpers up with #6, #18, or #20 wire approximately 6" long).

With ignition on, engine stopped, reinstall TPS adjustment screw and with Tool BT-7967A or equivalent, turn screw to obtain specified voltage at specified throttle position with A/C off. Refer to vehicle manufacturer's service manual or AC-Delco Tune-up Specifications Manual (SD-100) for specifications. g. After adjustment, install new plug (supplied in service kits) in air horn, driving plug in place until flush with raised pump lever boss on casting. NOTICE: Plug must be installed to retain TPS adjustment screw setting. If plug is not available, remove screw and apply Delco Threadlock Adhesive X-10 or equivalent to screw threads -then, repeat step f, above, quickly adjusting screw to obtain specified TPS voltage.