Q: Pedal and acceleration speed

Hi There, It sounds like you are describing the symptoms of a failing throttle position sensor. The throttle position sensor monitors the throttle position of the throttle plate inside the throttle body in relation to your foot position on the gas pedal. Based upon the inputs from the sensor reading your foot’s position on the pedal, the ECU then makes the direction to supply more or less fuel to the motor. When this sensor is not working properly, this can cause intermittent responses when pressing the gas pedal.

There are trouble codes that are typically associated with the TPS. One code will set if the TPS voltage is too high when the computer expects to see it lower. Another code will set if the TPS voltage is lower than the computer expects to see. The TPS code for low voltage is the most common and will usually set if the TPS is out of adjustment or the sensor has failed. The first thing you should do when you get a TPS code is to check adjustment and signal output of the TP sensor before replacing it. Be sure to wiggle all connections while watching scan data/voltage readout to make sure the problem is not a loose or bad connection.

There are circumstances that could occur with a failing throttle position sensor that may not set a trouble code. One of the most common symptoms of a failing TPS would be a tip-in hesitation or stumble when you apply throttle to take off from a stop. This can be caused by a dead spot in the TP sensor’s internal circuitry, which usually causes the output voltage signal to not change (or it drops out) when the throttle opens. Unfortunately this type of failure is not easy to diagnose without the proper tool – a digital waveform scope. Most digital volt meters and scan tool displays will not respond fast enough to show this type of a glitch; but some may. If you do find this fault, then the obvious fix is to replace the TP sensor. I would recommend having an expert from YourMechanic come to your location to diagnose and inspect your vehicle.