I have a 2010 Corsa. It has been fine for over 250,000 miles (400,000 km) and just passed MOT last month.

Driving home last night, it died on me. It was pulled out of a junction, got into 3rd when the revs went high for 5 secs before going back to normal. Then it got into 5th and revved high and smoke started coming from the back. I turned off the ignition and kept revving. There was black smoke from the back and white steam/smoke from the bonnet. She stopped and now won’t turn back on.

  • 3
    Does it use diesel fuel?
    – HandyHowie
    Commented Oct 9, 2023 at 5:55
  • 1
    How long did it run for while turned off?
    – HandyHowie
    Commented Oct 9, 2023 at 5:56
  • 3
    Yeah it's diesel and it went on for approx a minute Commented Oct 9, 2023 at 6:23
  • 6
    OT: passing an MOT test is no guarantee that the engine will run for 1 mile further. It only tests the legal requirements of roadworthiness and emissions. Commented Oct 9, 2023 at 19:15
  • 2
    To add to @WeatherVane's comment - plenty of people assume MOT'ing benefits you personally (i.e, tells you whether your car is in good nick or not), this is not the case. MOT'ing benefits the public by ensuring your car has a baseline of relative safety & emissions output deemed acceptable, an MOT inspector couldn't care less if the engine is about to grenade itself (at least, with respect to the MOT guidelines. Your average service tech would probably tell you if they actually spotted something worthwhile, but the overlap between what's checked on MOT and what could be wrong is tiny)
    – James T
    Commented Oct 10, 2023 at 12:47

1 Answer 1


Being a diesel and that the engine ran for a minute with the ignition turned off, makes it highly likely that you experienced diesel runaway.

During normal operation, diesel is used as fuel for the engine and turning the ignition switch off cuts the supply of diesel.

If an engine oil leak occurs where the leaking oil is sucked into the air intake of the engine, then the oil will act as a fuel for the engine instead of the diesel. The most likely place where the oil can leak from is the turbocharger.

Since you are in no control of this oil supply, the engine revs uncontrollably until the oil is used up, both starving the engine of lubricant and over-revving the engine.

It is highly likely that the engine is now wrecked and will need replacing, but there is a slim chance that it is reparable, so get it checked by a mechanic.

  • 6
    Sometimes it's possible to stop a runaway diesel engine by blocking the air intake with a cloth, though this shouldn't be attempted if you don't know exactly how to go about it. A runaway engine can be very dangerous.
    – barbecue
    Commented Oct 9, 2023 at 17:28
  • 21
    If the car is has a manual gearbox, you can shift directly into top gear; at below about 20 - 30 mph this will stall the engine
    – CSM
    Commented Oct 9, 2023 at 18:17
  • 4
    Another technique is to discharge a CO2 fire extinguisher into the intake to choke the engine of oxygen.
    – user71659
    Commented Oct 9, 2023 at 23:58
  • Goodness, there is no limit to the craziness of what can happen, or how you should handle it! I'm in awe. Commented Oct 11, 2023 at 15:45
  • 1
    @supercat Some modern diesel engines have ecu controlled throttles for emission control. If the throttle valve fully closes when the ignition key is turned off, then that would stop the runaway.
    – HandyHowie
    Commented Oct 11, 2023 at 18:12

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