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Steve, BMW Expert
Category: BMW
Satisfied Customers: 25231
Experience:  BMW Expert
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I have a 635i it is 4 years old. This morning it started well

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I have a 635i it is 4 years old. This morning it started well and drove for 15 mins before becoming sluggish when accellerating. It became progressively worse to the extent that it was very lumpy when idling. It won't now even try to start and is displaying a large ! Mark on the dash. No other warning lights are showing. Any one with an idea of the problem?
I will provide an honest answer. I trust this will be appreciated. Please remember that a low rating PUNISHES me for being honest and that I receive nothing for my time until a positive rating is clicked.
There are several things this could be. The most common would be a fuel pump or injection failure. Also a low battery, bad key or other immobilizer issue.
In terms of things you can try at home, I would suggest a second key, a jump start, and unhooking the battery for an hour to reboot all systems.
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.
Customer: replied 3 years ago.

Thanks Steve, don't think its i bad battery, the lights are bright so might try to take the battery off but will that result in me needing to enter any codes to get things to work? also if its a pump or injection problem what are the likely costs?


There are no codes needed if you unhook the battery. If you get a steering warning turn the wheel lock to lock a few times.
You are likely looking at around a grand if fuel system.
Please do not forget to CLICK ON a positive rating.
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