Thread: Hellish misfire
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Old 12-16-2023, 04:52 PM
Aidzer0 Aidzer0 is offline
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Hellish misfire

Hey folks!



I am the proud owner of a faulty N62 4.4l X5, with a constant misfire on cyl 7 and I was hoping one of you could help out.


To start the initial issue was a leaky plug tube, the tube seal was leaking oil into the plug and plug 7 was coated with burnt, flaky oil, which was mitigated with a brand new (Febi) tube and valve cover gasket, the car ran fine for about a month.


To which about a month ago, I got codes for multiple misfires on cylinder 5,6,7 with injector circuit open codes. I re-seated the injector connectors which was a "fun" task, but which helped cyl 6, no more code on cylinder 6. So I just bought 2 new injectors for Cylinders 5 and 7, replaced them, and I was still getting injector open circuit, I then tested the harness and noticed that 2 pins (for cyl 5 and 7) were not making contact, cool, ordered a harness, it came, I replaced, all of the codes for injector circuit open were resolved BUT the misfire on cylinder 7 remains.

From that point, I have taken the DME out, it of course, had oxidization on some pins, so I used contact cleaner and clean the connector side and the DME side, I also opened up the DME, tested the FETs and they tested fine. But still a misfire on cylinder 7.



Now we come to today, I decided to clean the coil harness and the ground points on the valve cover for bank2, I also replaced the brand new plug with another new one (all 8 were replaced 3 months ago after the valve cover job), I also tested 4 (brand new) coils, 4 different brands, 2 Bosch from different eras, 1 Delphi and 1 OEM from BMW, no luck there.



I am losing my patience with this thing, I have never had such a persistent misfire with so little information, I have access to tools like ISTA, BMW scanner and a regular OBD scanner, none of which show any relevant codes, and all the Lambda, O2 and MAF stats meet requirements of the DME, so its not sensor related (from what I can tell).



I would also like to add that the Fuel pump has been replaced by an OE unit from FCP (All parts are from FCP and I DO NOT use after market garbage). Also the vanos solenoids have been cleaned and tested, they work fine. I also made sure to re-learn the valvetronic motors before starting the engine after the VC replacement (Using ISTA).



For some back story, I have had a e46 for 6 years now, have done all the work on it myself from regular tuneups to code for a manual swap. I have had many many issues that have taken a few days to solve but this is going into a month of not being able to figure it out.

It misfires from start, until the engine is turned off, after the regular 60 seconds (I think) the DME shuts off fuel to Cyl7. I have also attached the freeze frame that I have from OBD Fusion.


Please, anyone suggest anything that I have not thought of, after all I am an M54 knower, I do not have a lot of knowledge of the N62B44.
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BMW 2006 X5 4.4l N62
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