Hellish misfire

[Aidzer0]

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I would also like to add that the Fuel pump has been replaced by an OE unit from FCP (All parts are from FCP and I DO NOT use after market garbage).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.

[EODguy]

Try your ISTA to verify code as "P" codes are generic and sometimes not what you think.

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[80stech]

I don't anything about the V-8s but you need to do a compression test. Maybe faulty new injector? Strange that you have/had so many injector harness problems??

[Aidzer0]

Originally Posted by EODguy

Try your ISTA to verify code as "P" codes are generic and sometimes not what you think.

Sent from Embassy network using Tapatalk

Prior I did read the codes and they revealed the same + cylinder shutdown due to the misfire and alternator code, but there is nothing wrong with the alternator... it is charging the battery just fine @ 13.6 - 13.8V. I do think it might be the comms wire to the alternator that is the issue, but that is not the cause for Cyl7 misfire (At least I do not think it is?) The battery is at a constant voltage and does not drop below the "regular" 12.7V (when powered off) and 13.6V when idling. I also did replace the alternator regulator and battery not too long ago (about 5 months now).

Cheers for the suggestions, I have decided to read the car again with ISTA just to be sure, SS is attached, along with some stats from INPA (I know it a bit better) Maybe these can give a hint to something? The Camshaft advance on bank2 is a bit high, not sure if this could be related or if its normal, seems to be out of spec by a few degrees?

Originally Posted by 80stech

I don't anything about the V-8s but you need to do a compression test. Maybe faulty new injector? Strange that you have/had so many injector harness problems??

That is my next test for sure! My in-law will be bring his compression tester here tomorrow and I will test it, I can say that I know the injector is firing now since I can smell the raw fuel being dumped out the exhaust. (This stops as soon as the DME shuts off Cyl7. So its not Fuel...

As for the injector harness... yeah... weird is all I will say... It might have been me though, when this first started I did put a needle connected my voltmeter to test continuity and I may have busted the pins on the harness side? Maybe? I do for sure know its on the harness connector and not the injector side that is the issue. Since I swapped the harness out, 0 issues with the injector open circuit and with INPA I can successfully now control each injector. Before swapping that harness, I could not.



A new development tonight, crank but no start... Never happened before, I was working on her earlier today, started a few times and had no issues, tried about an hour ago and she would not start at all, Had a few cylinders fire off and then it would just crank with no start. I tried 3 times and the 3rd time she started with the same cyl7 misfire... No new codes nothing new besides the no start.

[80stech]

Knock value up on 7 is worrisome but not necessarily a problem. Compression test will tell more. I'm not sure if it's a problem with these engines but a worn out cam lobe is something to keep in mind. Strange that 2 misfire codes and the alternator code got set at the same mileage and the adaptive headlite code 5 miles later.

[Aidzer0]

Originally Posted by 80stech

Knock value up on 7 is worrisome but not necessarily a problem. Compression test will tell more. I'm not sure if it's a problem with these engines but a worn out cam lobe is something to keep in mind. Strange that 2 misfire codes and the alternator code got set at the same mileage and the adaptive headlite code 5 miles later.

I believe the knock on Cyl7 is because of the cylinder shut off? Higher knock since the piston is being dragged rather than exerting the forces from combustion. (I am not sure thought...)

As for the codes, I was testing things, so I cleared them prior to taking the photo, the headlight level sensor and alternator have been an "issue" since we got the car 3 years ago, I have the headlight sensor ready to replace when warmer weather comes and the alternator regulator was replaced but the code is still there, as I mentioned, I believe its the comms wire that connects to the back of the alternator, I will troubleshoot that in warmer weather though.



I did stumble upon a thread that mentions incorrectly seated valve retainers after a valve stem seal job causing a constant misfire. And the behaviour looks the same as what I have on Cyl7. So this compression test will probably end with not great compression...


As mentioned earlier, today I will be getting a compression tester, I am hoping to be able to do the test today when we get back.

[Aidzer0]

Good evening folks!


So, I just came back from testing the compression on cylinder 7. its a whopping 0. Nothing, needle does not budge... it sounds like the exhaust valves may be open, But I do not understand how that is possible, I did nothing in the engine that would cause this all of a sudden...



Needless to say, I am lost for words and for next steps. Should I remove the valve cover to check if the valves are stuck open? Or a collapsed spring maybe?


Bare in mind, the garage is not heated and its 5F haha.



Thanks to all that have contributed this far!! Take care ya'll!

[80stech]

For sure take the valve cover off and have a look. I'm gon'na assume the rest of the cylinders tested good??

[Aidzer0]

Originally Posted by 80stech

For sure take the valve cover off and have a look. I'm gon'na assume the rest of the cylinders tested good??

Ouf, sorry, forgot to mention the others, they seem within spec, lowest was 149 and highest was 165. Lowest was cylinder 4.

[EODguy]

Fiber-optic cam could check valves.

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