Unsolvable misfire issue

Hoping the forum can help as I am exhausted and not sure what to do next...Sorry in advanced, this is a long one.

Long story short, I had no misfires before. Car was running perfectly.
Starting pouring some money into the car to bring it back to life. Installed new injectors. No problems, everything was great.

Couple of months after, I replaced my very leaky valve cover gaskets with new gaskets, alum covers, billet spark plug tubes/gaskets, and vanos covers.

Literally the day after install, I got a misfire code on a cyl. Swapped coil pack with another, code did not follow. This would happen a few times here and there, sometimes always on cyl one. Some times on 8. Other times it would just be a random cyl. I would "reseat" the coil thinking it just wasn't seated properly and then the code would be gone.

As the weather has gotten colder, the car will now go into limp mode with a "misfire" during every single start up. Its normally always CYL 1 or CYL 8.
I learned that If I let the car come up to operating temp and either restart the car or clear the code, the car would drive fine for the rest of the day. No more misfires.

If the car sat overnight, misfire would happen again the next day until the car got up to temp and then restarted.

Now the car has gotten to a point where it will throw a misfire code no matter what. I can clear it but it will come back within 30 seconds of starting the car.

I have moved the coils and plugs around and the code does not follow. I have checked grounds on the covers and both are tight. Car has a new battery that has been registered. The spark plug on CYL 8 had some oil on the threads which makes me think that the spark plug tube gasket rolled during installation, but I am not sure this would cause this misfire. This is also the only spark plug that has oil on the threads, so it doesn't explain why CYL 1 will "misfire" as well. I cleaned the oil of the spark plug threads, put the plug into a different cyl but cyl 8 still continues to misfire immediately.

Lastly, there has been one or two scenario's recently where the "misfire" and limp mode have come on but I was not able to stop and reset the car right away. During this drive, its like the "misfire" would clear up and the car would run perfectly. I would stop the car to check the codes and as I would turn the car back on, the misfire and limp mode would come back.

What is everyone's thoughts or recommendations? I have a laptop on the way so that I can install BMW tools, but in the meantime what should I check?

I'm on the verge of sending the car to the shop but I know this has got to be an issue that I created during the VCG job seeing as these issues started the day after. I'm just so lost and exhausted as this point as I have been chasing this for months.


To recap:

New VCG, Valve cover, Vanos covers, Injectors (installed months prior).
Code(s) do not follow coils or plugs if swapped around.
Checked grounds on both valve covers.

This engine management system uses the spark plugs to detect knock. if you have oil in your spark plugs start there

spammysammich wrote

This engine management system uses the spark plugs to detect knock. if you have oil in your spark plugs start there

The oil that was in the tube was such a minimal amount and I believe it was just from reassembly of the covers. That's just how small of an amount it was. I will double check that the tube is dry again though.

As for the plug on CYL8 that had oil on the threads, I cleaned the oil off, swapped it with cyl 6 to see if it was the plug and the misfire did not follow.

Thank you for your advice!

What about the condition of the chassis ground at the left side near the header? Double check the wiring harness for possible damage as you have to swing that out of the way.

If the misfire stays, grant you might be having it intermediately on 2 cyls.

I know you said you swapped coils/plugs, did you try swapping injectors?

Once those are ruled out, I'd say it's time to scope the cylinders and/or do a compression test.

Small update.

Car has been misfiring for the last two weeks on cyl 5 only. I moved the coil to cyl 6 and it did not follow. So I assumed it had to be the plugs.

Thinking I finally solved the issue, I installed new plugs, turned the car on, misfire on cyl 5 gone, but now misfire on CYL 2 is there.

What are your thoughts on it possibly being the donut gaskets after the headers/before 02 sensors?

Chaszm wrote

Checked grounds on both valve covers.

It is a long shot, but I would fix these grounds properly to rule them out and because it might help, and it's just a good idea.

All S65 aluminum valve covers suffer from coil grounding issues. You need to file/sand through the powder coating or anodizing to get to bare metal for a proper ground connection in a specific spot for each cover. I may be the first and only person to do this so far, but I am hoping an educational campaign will change that.

It sounds like you've only checked these grounds for tightness. The ring terminals should be wire-brushed and the mating surfaces raw aluminum and brushed as well.

You also never followed up on the engine grounds mentioned by spammysammich. It could still be those.

What plugs did you use? Are they the exact plug required for the car or some fancy material like ruthenium or iridium? They have to be the recommended plug, platinum LKR8AP. Anything else will cause random misfires.

Check the wiring harness grounds on each valve cover by ensuring metal to metal contact i.e. clean, and preferably sand each side of the connections (cover and harness rings). The head of each coil pack contains a solid state circuit board. Consequently, if any cracking or stress damage occurs to any of the coil pack heads and/or the harness to coil pack wire connectors - misfires can occur. Removal and installation of the coil packs takes patience and care. The best method described on this forum is to use a thick shoelace inserted between the valve cover and the bottom of the coil pack head i.e. around the coil pack body - then pull upwards along the directional line of the coil pack body. Other methods such as using the button on the head of the coil pack with a puller, or using screwdrivers to lever up on the coil pack heads, can crack the coil pack heads. Anyway, proper installation requires the coil packs audibly "click" back into place on top of the spark plugs or you feel them click back into place properly.

Must Do:
1) Check all the coil pack heads for damage or cracks
2) Verify metal to metal harness to valve cover contact on both valve covers
3) Ensure all pf the coil packs are properly seated on to the spark plugs
4) Visually verify the integrity of all of the individual harness to coil pack connectors
5) Check for oil leaking into the spark plug wells
6) Ensure each coil pack wiring harness connector is "clicked" in and properly connected to the coil pack

Optional:
1) Install new spark plugs

BenFenner wrote

It is a long shot, but I would fix these grounds properly to rule them out and because it might help, and it's just a good idea.

All S65 aluminum valve covers suffer from coil grounding issues. You need to file/sand through the powder coating or anodizing to get to bare metal for a proper ground connection in a specific spot for each cover. I may be the first and only person to do this so far, but I am hoping an educational campaign will change that.

It sounds like you've only checked these grounds for tightness. The ring terminals should be wire-brushed and the mating surfaces raw aluminum and brushed as well.

You also never followed up on the engine grounds mentioned by spammysammich. It could still be those.

I could kiss you right now. This was the issue. Took some 180 grit sandpaper to the cover. Misfires are completely gone. Thank you so much!

I have to admit, I'm kind of astounded myself that the issue was the poor coil grounds to the valve covers. Here's hoping you did find the true issue and the fix lasts! \m/

Chaszm do you have an update for us? Still all good?

BenFenner wrote

Chaszm do you have an update for us? Still all good?

Unfortunately, no. I still have a CYL 2 misfire during every start up. Sometimes it clears up after driving a bit, but limp mode/misfire will kick back up during driving at times.

Sanding the covers down fixed all the random misfires though.

So far I have:
Installed new spark plugs (OE Spec)
Installed new Coil
Sanded down finish on valve covers
Pull valve cover to ensure spark plug tube gaskets were not rolled
Swapped Coil/Plug with another cyl to see if code follows (it does not).
Fuel injectors were replaced less than a year ago (I would not think this is faulty unless the valve cover grounds somehow killed the injector?)


This weekend I plan to swap the injector with cyl 1 to see if it follows. If it doesn't, I want to think its something with the injector harness wiring or possibly the coil plug/wiring. Its just hard for me to believe its the wiring seeing as the misfire clears up once the car is up to temp or its warmer outside.

I recently picked up an MHD scanner for my other 3 series so I do have access to protools now. I am not sure if anyone is familiar with it and if there are any tests or live data options that I can use to help narrow down my issue.

Seeing an continuity isnt an issue and it doesnt seem to me like its DME related, i would swap out that valve cover on that bank for a stock one.

amrazM wrote

Seeing an continuity isnt an issue and it doesnt seem to me like its DME related, i would swap out that valve cover on that bank for a stock one.

If I had a spare, good condition cover, I would try that.
My were absolutely trashed and got recycled though.

how does the plug look from cylinder 2? did you try moving the injector from cylinder 2? couple of things left to check here, there is a chance you have a bad injector.

amrazM wrote

how does the plug look from cylinder 2? did you try moving the injector from cylinder 2? couple of things left to check here, there is a chance you have a bad injector.

I plan to move the injector this weekend to see if it follows. I will pull the plug as well.

Chaszm wrote

I plan to move the injector this weekend to see if it follows. I will pull the plug as well.

I suggest you scope the cylinder if you have access to a borescope and plug is out.

Chaszm wrote

I plan to move the injector this weekend to see if it follows. I will pull the plug as well.

report back

Check cyl 2 valve spring.

Redd wrote

Check cyl 2 valve spring.

i was getting at that, wasn't trying to panic him

Chaszm wrote

I want to think its something with the injector harness wiring or possibly the coil plug/wiring.

These would be my next suspects if it does not end up being the injector itself.