Symptoms suggesting a bad TPS:
* Poor Idle: Rough idle, stalling, or an idle that fluctuates wildly. This is a very common symptom.
* Hesitation or Stuttering During Acceleration: The engine may hesitate or stumble when you accelerate, especially from a stop.
* Poor Fuel Economy: A malfunctioning TPS can lead to a rich or lean fuel mixture, impacting fuel efficiency.
* Check Engine Light (CEL): A CEL will likely illuminate, accompanied by a diagnostic trouble code (DTC) related to the TPS. You'll need a code reader to get the specific code.
* Transmission Issues (Automatic): On automatic transmissions, a faulty TPS can cause shifting problems because the transmission relies on TPS input for proper shifting. This might include delayed shifting, harsh shifts, or slipping.
* No Spark (less common): In some cases, a severely faulty TPS can prevent the engine from generating spark, leading to a no-start condition. This is less frequent.
Important Note: Many of these symptoms can also indicate other problems, such as a faulty mass airflow sensor (MAF), vacuum leaks, ignition issues, or problems with the fuel system. Therefore, simply observing these symptoms is *not* enough to definitively diagnose a bad TPS.
How to Confirm a Bad TPS (requires tools and some mechanical knowledge):
1. Read Diagnostic Trouble Codes (DTCs): Use a code reader to check for trouble codes related to the throttle position sensor. This is the first and most important step.
2. Voltmeter Check: This is the most reliable method. You'll need a voltmeter. With the engine off, check the voltage at the TPS terminals. The specifications (voltage ranges at different throttle positions) are usually found in a repair manual for your specific vehicle. You'll need to disconnect the TPS connector, and carefully test the voltage at the sensor terminals while manually moving the throttle plate. The voltage should change smoothly and progressively as the throttle opens. Any erratic readings, jumps, or failure to register voltage changes strongly suggests a bad TPS.
3. Visual Inspection (less reliable): Carefully inspect the TPS connector for corrosion, loose wires, or damage. This is only a preliminary check and doesn't guarantee a faulty sensor.
In short: While the symptoms listed above *hint* at a possible TPS problem, they are not conclusive. You absolutely need to read the DTCs and perform a voltmeter test to accurately determine if your TPS is faulty. If you're not comfortable performing these checks, it's best to take your vehicle to a qualified mechanic for diagnosis and repair.
