Skip the auto shop - Our mechanics make house calls

Q: Why does my car jerk & accelerate by its self?

asked by on

My car recently started accelerating by itself when in parking gear. It doesn't do it so much in drive but when you completely turn off the ac it accelerates & de-accelerates. My car also jerks like little jerks & only sometimes, like when at stop signs.

My car has 160000 miles.
My car has an automatic transmission.

From what you’ve described, the jerking is most likely due to a misfire or a vacuum leak on the engine. You should have all the spark plugs and wires checked for misfiring after your computer is scanned for a misfire code.

You may have a leaking valve cover getting oil on the plugs and wires. Another possibility is that the engine may have a vacuum leak, causing the high idle and even the misfire if no other problems are found. A proper diagnostic should be done if any engine codes are present.

If you need help with getting this fixed, consider YourMechanic, as one of our mobile technicians can come to your home to diagnose the misfire firsthand for an accurate repair. Best of luck.

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!
  1. Home
  2. Questions
  3. Why does my car jerk & accelerate by its self?

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: No check engine light

Considering your symptoms, I would suspect that your issue lies within the fuel or ignition system. Without diagnostic equipment, it would be best to have your vehicle inspected by a technician who does. Although you have no Check Engine Light,...

Q: Clutch line not bleeding

The clutch and brakes don't use the same master cylinder. They both use brake fluid, but that is the only things they have in common as far as parts go. The clutch will have its own master cylinder, line and...

Q: 2003 Kia Sedona starts and runs for one minute then dies. Restarts and does the same thing. Threw a code the other day of cylinder

Hello. Thank you for writing in. At first the issue sounds like an electrical problem. There are a number of sensors that will cause the engine to stall. Some of them are not monitored by the computer and will not...

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...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
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...