Q: Poor acceleration and rough idling at times.

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Truck is idling rough at times and has poor acceleration and sometimes none at all. Replaced plugs, wires, pcv valve, fuel filter and pump. New muffler and cat. Starts up fine but driving it is almost impossible. It acts like it isn't getting fuel properly and when it starts sputtering if I floor it, it just quits altogether.

My car has 160631 miles.
My car has an automatic transmission.

This may be related to a dirty or failing idle air control valve, or throttle position sensor.

The idle air control valve is a unit that reads the air intake as it is mixed with fuel, prior to being injected into the motor. The computer uses this information to make fueling adjustments. When this valve does not work properly, it may cause an over-fueling or under-fueling situation, depending on the conditions, which may cause a rough idle or poor acceleration.

The throttle position sensor is a sensor used to monitor the throttle position of the throttle plate inside the throttle body in relation to your foot position on the gas pedal. The sensor is usually located on the throttle plate so that it can directly monitor the position of the throttle. The ECU then makes the direction to supply more or less fuel to the motor. When this sensor is not working properly, it can cause intermittent responses when pressing the gas pedal.

It is recommended that you get a professional technician, such as one from Your Mechanic, to come to your location and diagnose your throttle control system and replace the idle air control valve, if needed.

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