How to Set the TPS on a 1986 Ford Mustang

The TPS sensor in your 1986 Ford Mustang provides a variable resistance signal to the on-board computer that indicates throttle position. This signal along with MAP (manifold absolute pressure) and EGO (exhaust gas oxygen) is used by the computer to determine engine load. After engine load is calculated, the computer can accurately control fuel and ignition timing requirements. The key to adjusting the TPS correctly is to understand that the throttle's minimum air rate must be correct before adjusting the TPS.

Tools Used: Digital voltmeter, Screwdriver, Torx driver

Set the TPS

Start the engine and allow it to run until the temperature on the Mustang's temperature gauge is in the normal range. Turn the engine off.

Unplug the electrical connector from the idle air control (IAC) valve, which is located on the throttle body. In the 1986 Mustang, the IAC valve is a cylindrical-shaped component located on the front of the throttle body facing the front of the car. Start the engine.

Locate the idle-speed screw on the bottom of the throttle body near the throttle linkage. Turn the idle screw using a T-15 torx driver until the idle speed with the IAC valve unplugged is approximately 650 rpm on the car's tachometer to adjust the minimum air rate. Access to this screw is easiest from the rear of the throttle body on the Mustang. Turn the engine off and reconnect the IAC valve's electrical connector.

Turn the ignition key to the "Off" position. Set your digital voltmeter to read the "TPS 5" volt signal by turning the dial on the meter to the 12-volts scale. Attach the black (ground) lead of the meter to the negative battery terminal.

Locate the TPS on top of the throttle body. The Mustang uses a three-wire TPS. The black wire is ground, the orange wire is a 5-volt reference signal and the green wire is the TPS signal. Insert the red (positive) lead of the meter into the back of the TPS sensor's electrical connector at the "Green" colored wire until it touches the terminal in the connector.

Turn the ignition key on and observe the voltage reading on the meter. The Mustang's TPS should be adjusted so that the voltage on this terminal is 1-volt +/- .10-volt. Adjust the TPS by loosening the two small screws that attach the TPS sensor to the top of the throttle body and rotating the TPS until the voltage on the meter reads 1-volt +/- .10-volt.

Tighten the TPS screws snugly. Turn the ignition key to the "Off" position and disconnect the voltmeter from the car. Loosen the negative battery cable using a 13 mm wrench and pull the cable off the battery. Wait 10 minutes and reconnect the battery cable. This will reset the computer and clear the trouble code that was triggered during the minimum air rate adjustment.

Test drive the car and verify that the adjustment is correct. The engine should idle smoothly and there should be no hesitation or stumble during acceleration.

Tips & Warnings

Wear safety glasses and work gloves when working around a running engine to prevent serious injury.

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