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Q: Slight jerk when changing gears, especially when starting from a complete rest.

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When I move from ZERO, you can notice the car is changing gears, the changeover is noticeable and in jerks. Is this normal for this type of car?

My car has 100000 miles.
My car has an automatic transmission.

A: This may be a sign of a failing mass air fl...

This may be a sign of a failing mass air flow sensor or a throttle position sensor. The mass air flow sensor is a unit in the intake system that monitors air intake as it is mixed with fuel prior to being injected into the motor. When this fails, this can cause an imbalanced air/fuel load to be supplied to the motor which often times results in the engine starving for air or fuel. This is what causes the hesitation or loss of power you describe. This can also cause the engine to struggle to idle for the same reason.

The throttle position sensor (TPS) is a sensor used to monitor the throttle position of a vehicle. The sensor is usually located on the butterfly spindle/shaft so that it can directly monitor the position of the throttle. This sensor relays the position of the throttle plate (also called the butterfly) relative to your foot’s position on the gas pedal and associates the two in the ECU. 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 applying the gas pedal. If you need some help with getting this fixed, I would suggest having a professional from YourMechanic come to you home to diagnose the jerking symptom you’re experiencing and test drive your car to correct the problem.

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