How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Steve Your Own Question
Steve, BMW Expert
Category: BMW
Satisfied Customers: 25242
Experience:  BMW Expert
Type Your BMW Question Here...
Steve is online now

MY X3 has just ground to a halt. The engine warning light came

This answer was rated:

MY X3 has just ground to a halt. The engine warning light came on and there is a lot of black smoke from the exhaust. Under the bonnet there is a high level hiss of air from the drivers side of the engine (I cannot see from where because of the engine cover. There is also some black smoke from under the bonnet when you touch the accelerator. There is little or no pressure in the engine for moving the vehicle. Can you tell me what you think it may be?
what events preceded the smoke? what is compression on each cylinder?
Customer: replied 4 years ago.



To be honest, I haven't checked the compression on the cylinders. The car had been a bit sluggish but I put that down to the colder weather, once warmed up she was normally fine. We took her out for a drive and the engine light went on and she skipped into limp home mode, I got her to a lay by but by that time the smoke was there and then the hissing from the engine bay. There does not appear to be any leaks from the engine of oil or water so I am really not sure. We live in the North of Scotland so before I get her towed to a garage I wanted an idea of what I am up against.

a hiss would usually be an air leak or failed valve. the covers need to be removed to verify the source.


black smoke from the exhaust would normally be due to an over fueling issue which could be due to a bad airflow or temp sensor or injector or fuel pressure issue.


black smoke from under the bonnet again indicates a leak of some kind, which would need to be again verified visually or with a pressure test or smoke test.


since the engine light is on, the other important step is to have the fault memory read out from the car's computer.


Sorry if you were hoping for a different answer, please don't shoot the messenger - I can only give the honest answer, which I have. Please remember that a low rating PUNISHES me for my honest and prompt response, and I receive nothing for my time and answer until a positive rating is clicked.

Please let me know if you have further questions. Please do not forget to click a positive rating as this is the only way I receive credit for my answer, thank you. Best wishes with your vehicle.

Steve and 2 other BMW Specialists are ready to help you
Customer: replied 4 years ago.



Thanks, XXXXX XXXXX the answer and I know it can be hard when you cannot see the vehicle or the symptoms. I will give you a good rating, at least I have a little information to discuss with the garage so it looks like I know what I am talking about!!