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I have a big problem whit my 2.0 Bmw e46 320d. The problem is that I was driveing one night and the car gust started revving by itself around 7k rpm the car had so much boost at the time that I almost crashe. I puled over and the car was still reving,I tryed to stop the car by pulling out the key and turning it off , the car was still running by itself whit the key in my hand.After a few minutes the car stalled. After that I tryed starting it again and the same thing happend. i needed to call a trailer to move my car out the way.

That was a scary situation for me.

If you have any advice and cnow what caused the problem and what can I do to fix it please help me out. Thank you.

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  • Welcome to Motor Vehicle Maintenance & Repair! Dec 15, 2023 at 17:36

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This sounds like what is typically called a diesel runaway. Since all diesel engines need to keep going is fuel and air, it can easily happen if there's a problem with the turbocharger leaking oil. As long as there's oil in the system, it can keep running at high RPMs until there's no oil left, even without diesel being injected into the engine. The turbo leaking oil is one way, but there's other ways it can happen too, such as if the governor goes haywire and allows an unlimited amount of fuel to be injected. This is a LOT less common than a bad turbo seal, but is still possible.

In order to fix a turbo, if this is what has happened, you would either need to get the turbo in the vehicle rebuilt or replaced.

I wouldn't be surprised if the engine has suffered some type of damage. To be run at that high of an RPM for any amount of time will bear a toll on it. Even once whatever caused the runaway on the engine is fixed, you may find out there are now larger problems with the engine, so don't be surprised.

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