Originally Posted by Bmw135er
Definitely double check the hold down straps installation. As you are well aware, that's the peak boost window on the N54 and the highest load as a result. If that checks out okay and you're hesitant to want to pull the valve cover, try swapping a known good set of coils and plugs from another car. Injector misfires are usually on cold start in my experience. The mileage seems to be low for excessive carbon build up I cause a misfire. It's more likely you got a bad part off the shelf than extreme carbon build up.
Those straps are definitely oriented properly. I had 1, 2, 5, and 6 out, and the bow for 3-4 is definitely correct. There's no signs of the injectors rattling around, trading metal, or damaging the injector seal bore or the step on which the decoupler element sits.
Bad part is possible, but before the car first came in, the problem was persistent on cylinder 5. New plugs from BMW, still on cyl 5. New coil on cyl 5, still misfires on 5. Then the customer brought it to us. So I did my own tests, moved coil, plug, and injector. The misfire was still persistent on 5. After moving all that stuff around, finding the sooty tip on injector #1, replacing that injector, and putting it all back together with all the proper new seals and decouplers, etc, now it doesn't want to set a code for misfires, even though they're painfully apparent.
I think the VC gasket or whole VC plus the regular maintenance of intake intake cleaning is the next best step. Checking leakdown and compression will be a snap at that same time, too, so I'll definitely check that.
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