Throttle Position Sensor

Inspect/Test/Service

Different kinds of problems can happen with a throttle position sensor (TPS).

  • The most common symptom of a bad or misadjusted TPS is hesitation or stumble during acceleration.
    • The fuel mixture leans out because the computer does not receive the right signal telling it to add fuel as the throttle opens.
    • Eventually, the oxygen sensor senses the problem and adjusts the mixture, but not before the engine stumbles.
    • On carburetor and TBI systems, fuel can migrate into the sensor.
  • In cold weather a TPS gets cold and the feather (wiper arm) sometimes does not wipe against another metal strip.
    • If the strip wears away, momentary interruptions of the electrical signal can occur. These interruptions are called glitches.
A throttle position sensor has a wiper arm that rubs against a resistor strip.
  • When the engine is under a heavy load, the air conditioning compressor is shut off by the computer. A bad TPS can shut off an air conditioning compressor.
  • Also, on computer controlled cars, the key should be turned on before depressing the throttle or the computer can receive a faulty TPS reading and the car might not start.

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