[willisodhiambo]

So a friends car F10 528i started with consistent cylinder 5 misfire occurring only under WOT. Car would shudder but get back to normal with normal driving. Over time it began to go into limp mode and would return to normal on restart. The misfire is worse as in it is now consistent and easy to trigger with spirited driving.

Coils swapped, no change, plugs swapped, no change, injector no 5 replaced with another from similar engine, no change. Compression tests OK, cylinder head cover changed. Inspected the intake thinking it could be the infamous coking of turbo engines. This one is sqeaky clean (528 being NA)! We are at our wits end. What comes to mind now are,

1. Faulty DME
3. Faulty harness
2. Worn or faulty compression ring

Anything else one can look for before the painful decision to dismantle the engine or replace a working DME? I just cant see what is special with cylinder 5 other than mechanical fault.