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Car made a rumbling sound when turned off?

When I turned off my 1999 Toyota Corolla yesterday afternoon, I noticed that it sounded as if the car was still running. The car was shaking and making a low rumbling sound, even though the key was out. I thought maybe I did not turn off the car completely. So, I put the key in and turned the car on. The weird sound disappeared. I then turned the car off and took out the key, the car made the same rumbling sound and shaked. I tried again and confirmed that it was my car making this weird sound. The only way to make the weird rumbling sound gone away was to keep the car on. I did so, and called for help. Then, I noticed smoking came out from the left front hood. Somebody passed by helped me turn off the car. The key was stuck inside the keyhole this time, but the rumbling sound went away. Someone else opened the front hood and saw lots of smoke, but no visible fire. At this moment, we were able to take the key out of the keyhole, even though the power window was no longer powered. I left because I was scared the car was going to explode or something. Do you know what is wrong with my car? How can I fix it? Actually, yesterday morning when I was starting the car, I noted that it was hard to start it. I tried 7 times and finally succeeded.

My best guess is that the engine is “dieseling”. This means that superheated carbon in the cylinders is allowing gasoline to continue to be combusted after the ignition is shut off, although the combustion is very uneven. While I would not describe the sound of a “dieseling” engine as “rumbling”, descriptions of sounds are very individual. Another clue to dieseling is very foul exhaust fumes while this phenomenon is taking place.

Because this phenomenon is not supposed to be able to take place on a modern fuel-injected car with an electric fuel pump, I cannot guarantee that the engine is actually dieseling. However, I can tell you that this phenomenon is possible when an engine has not been maintained properly over a period of years. If your car fits that description, then I suppose that it is possible for this to happen, even if the car has an electric fuel pump and fuel injection.

The clues to poor maintenance include your difficulty in starting the engine. My best suggestion is, if you can start it, drive it to a well-reputed mechanic and let him see what happens when you turn the ignition off. If it cannot be started, then you have no choice but to tow it to the mechanic. Unfortunately, engine problems do not cure themselves, so a mechanic’s intervention will be needed, no matter how you get the car to him.

Thanks very much for the prompt reply and your input! I will definitely take the car to a mechanic. I am just not sure who I shall go to since I am new to this city and how much it will cost.

Ask friends, neighbors, co-workers, and relatives for recommendations on an independent mechanic’s shop.

DO NOT go to Midas, Meineke, Monro, Sears, AAMCO, Pep Boys, or any other chain operation unless you are willing to risk unnecessary, overpriced repairs, coupled with poor workmanship.

You might want to try the Mechan-X files on the Car Talk website for recommended mechanics in your area.