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Matt, Mechanical Engineer
Category: BMW
Satisfied Customers: 116
Experience:  BEng hons Mech engineering, in auto industry 22 years
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We have a 2007 BMW 120i (manual gearbox) with constant misfire

Customer Question

We have a 2007 BMW 120i (manual gearbox) with constant misfire problems.
In the last four years, it has broken down (gone into limp home mode) about 10 times. We used to take it to various BMW main dealers (it was under extended warranty) and they replaced:
All four injectors
All four coils about 6 times
All four plugs about 3 times
Each time they replaced the coils, it felt better for about a month, and then gradually it would have more and more misfires until it got to the stage that the engine warning light would come on and we had to go back.
Right now it's really bad. Under normal driving conditions it is OK, but if you try to accelerate in a high gear (for example - heavy throttle in 4th gear at 20mph) it will stutter/misfire really badly for a few seconds and then the engine warning light comes on and fuel is turned off to one or two cylinders.
All four cylinders are affected (it is random which one stores a code in the computer, but they have all done it). We have just had the coil packs in cylinder 1 and 4 replaced, and on the drive home it flagged up a misfire warning for cylinders 3 and 4!
What should we do next to try and resolve this?
Submitted: 3 years ago.
Category: BMW
Expert:  Steve replied 3 years ago.

what is compression for each cylinder?

Customer: replied 3 years ago.

How would I check that?

Expert:  Steve replied 3 years ago.
With a compression guage