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Q: Jerking when accelerating (after slowing down).

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Hi mates, I am just wondering if you can help me out with the jerking issue on my 2007 Foresters. When I accelerate from a complete stop, there's nothing wrong, no matter how hard I hit the accelerator. However whenever I slow down to around 16-17mph and then accelerate, there will be a short moment of hesitation before it jerks (it sounds like the car got confused, doesn't know which gear to shift and then decides to down shift too quickly, making a big shock/jerk). Some mechanic told me that could be the transmission, others said the engine that acting up which make me more confused. Do you have any suggestion on which to look at? I know a bit about some technical so hopefully can understand your advanced analysis. Thank you for your help. Cheers, Hugh

My car has 110000 miles.
My car has an automatic transmission.

A: Hi there. From my experience with this vehi...

Hi there. From my experience with this vehicle the issue is almost always a failure in the throttle body. It is very common for the throttle body to have an intermittent failure and for it to run like this. Most of the time it is because of a flat spot in the throttle body motor which causes this strange hesitation that you have.

I typically test the throttle body with a scan tool to monitor the sensors on the throttle body as will as from the accelerator pedal sensors. There were also issues with this throttle body which causes it to eventually fail completely. It can also be caused by a dirty fuel injector or carbon build up in the engine but that is not as common.

If you’d like to have this repaired, consider YourMechanic, as one of our mobile technicians can come to your home or office to diagnose your jerking symptoms and help you make the necessary repairs.

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