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Q: My car is accelerating on its own.

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Once I start my car it start to accelerate on its own , like if someone is pressing the gas , if I put it in drive the car starts picking up speed & its hard to brake . I feel like I'm steping on both at the same time .

My car has 140000 miles.
My car has an automatic transmission.

A: Inasmuch as you are writing in about uncomm...

Inasmuch as you are writing in about uncommanded (aka, "unintended") acceleration, I can tell you the National Highway Traffic Safety Administration, one of the Federal agencies that tracks vehicle defects, would love to hear from you. You can file an on-line complaint at their website www.NHTSA.gov (go to https://www-odi.nhtsa.dot.gov/VehicleComplaint/ ) or call in the Complaint to the NHTSA Vehicle Safety Hotline (Toll-Free: 1-888-327-4236 / Hearing Impaired (TTY): 1-800-424-9153).

Engine speed is dependent on the amount and rate at which air and fuel are admitted by the engine control systems into the combustion chambers. Based on the NHTSA complaint database, and other sources, relative to your specific year, make and model, I would recommend testing your idle air control (IAC) valve as well as cruise control system. Both of these systems have been implicated in the type of symptom you are describing.

If the problem is not found in either system, since you are describing this as a non-intermittent problem, it should not be too hard to narrow it down just by looking sequentially at each and every other component that controls the "rate" at which air and fuel are admitted to the intake system. While this issue remains unresolved, obviously you have to exercise caution and just remember that, if faced with wildly uncontrolled acceleration, simply turn the ignition switch to the off (but NOT "locked") position and then place the car in neutral, while being mindful of your surroundings and adjacent traffic.

I recommend having a certified mechanic, such as one from YourMechanic, come to your location to determine why the car is accelerating without cause and replace the idle air control (IAC) valve or inspect the cruise control system.

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