Q: My car is still running after turning it off.

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I just replaced the battery yesterday. I went to work got there with no problems. I parked it and turned it off. But it sounded like it was still running, I tried to start it again and it wouldn't start. It ran with the car being off for about 10 minutes and then I started to see smoke after about 12 minutes it stopped running but still wouldn't start back up.
My car has an automatic transmission.

Hi there. The noise that you are hearing is commonly known as ’Dieseling’. When this happens, check the ignition switch alignment and see that the switch is turned completely off. If the switch is turned off, then while the engine is still trying to run, disconnect the power to the ignition coil pack and the engine should stop running. If the engine stops running, then there is power feeding from the ignition switch to the ignition coil after the switch is turned off. If this is happening, then the ignition switch needs replaced. If the engine continues to run with no spark, then there is too much carbon deposits in the combustion chamber. I recommend putting sea foam in the fuel tank, the engine oil, and the vacuum system, but one section at a time. This will help clean up the carbon deposits and allow the engine to stop dieseling. Carbon deposits get very hot and stay hot for a long time. When fuel is entered into the chamber, the carbon could ignite the fuel at an earlier time, or even after the injector has stopped running. Oil that has fuel vapors in it will continue to burn when the carbon is hot, keeping the engine running. If you need further assistance with your engine running after turning off the ignition, then seek out a professional, such as one from Your Mechanic, to help you.

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