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.