Skip the auto shop - Our mechanics make house calls

Q: Poor acceleration and rough idling at times.

asked by on

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.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: My 2010 Ford Escape vibrates a lot. There are no leaks at all. What could be the cause?

If the vibration happens when you're stopped at a red light, then it's more than likely caused by a vacuum leak, or fuel or ignition system component failure. Typically, the first three parts that would be inspected are the idle...

Q: When I rev it it has a hard time.

This is tough to diagnose without more info, however it could be potentially some things like a faulty mass air flow sensor or throttle position sensor. Either of these two parts will have a negative impact on fuel/air flow which...

Q: Leaking antifreeze

The leak you are describing is the radiator core leaking. You should have the system pressure tested to see if the radiator core is leaking in the center or the side tank is leaking.

Related articles

How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.