[Fabmex]

Hey guys,
I have another topic for the misfire specialists here. I promise I have read all I could on the fórum with the search engine and I do not think there was a similar case reported in the past.

It started a few months ago with what appeard to be the now "classical" misfire issue. I had alternatively cylinders 4 5 and 6 misfiring. It always left after a while but never for long.
So I replaced all 6 coils and it seemed to solve the issue for a Little while.

Unfortunately it is coming back hard on me now. This morning was worst than ever before. Car couldn't even stay at idle for long and I had misfire on all 3 cylinders (4,5 and 6 again) at the same time with as you can imagine a lot of smoke due to unburnt fuel. Of course al sort of different messages came on.
Then it hit me. This is ONLY happening on cold mornings. It never happens to me when I leave from work. Always in the morning and only on cold mornings. By cold mornings, I mean 40° and below.

So I let my engine heat up, and one by one the misfires disappeared until all went back to normal when engine oil reached 175°.

So that's my story, what do you think? What would cause a misfire only in cold mornings, considerng coils are new?
Many thanks in advance for your help, weather forecast announces 32-35 for tomorrow morning.

[Fabmex]

Quick update from tonight coming back from work.
As planned engine started just fine since it was not cold.
I just noticed that at cruising speed, low rev, when accelerating a little, low throttle, engine kinda have some hick ups. They disappear when pushing it harder.

[AdamN52]

Have you checked/replaced your plugs?

Could be a broken wire/loose connector? As the engine bay heats up the conductor would expand and make good contact. I've seen it happen on a friend's car (non-bmw). The harness connector leading to the coils had a pin loose and intermittently caused misfires, and it was worse when cold.

[Fabmex]

Seems like a reasonnable hipothesis.
I'll try to check if something is loose on the 4,5,6 cylinders connection this week-end

[AdamN52]

Originally Posted by Fabmex

Seems like a reasonnable hipothesis.
I'll try to check if something is loose on the 4,5,6 cylinders connection this week-end

Figure out your issue?

[BashShah]

I think you have Multiply issues.
But primary is Carbon Build up on the intake ports.

I recommend the following: (all of the below)
1) Walnut Blast (Or at least Bore scope each port to see how bad it is.) I am leaning here.
2) Change your Plugs, if you did not.....when you did the coils.
3) Run 2 Cans of BG44K 1 after the other on 2 Tanks to rule out Injectors being clogged due to Bad Gas.

The last one, but I doubt it.
Vanos Solenoids, clean em swap em, or replace them.....but I doubt it as causing anything.

Why do I state the above, cause I wend through this Last winter.
Now, this winter, a hell of a lot less.
During cold start, only today, I heard, measurable repeated very slight mis fire.
1 Miss Fire every 3 sec, but no DTC codes....fuck.

I honestly think that these cold start Miss Fires are part of the ecm programming during cold start this should have been an issue that BMW should have addressed long ago like many others but never did.
But a Walnut Blast really did wonders for my issues, and I changed my Vanos after that, as it through a code....that did nothing.
Then I replaced the spark plugs, and it helped a little more, then I replaced the coils, and wow....I had a hard time wondering what is a miss fire.

Regards,
DN

[Fabmex]

Thanks for your feedback Dark Nemesis.
I have read a lot lately on that Walnut blast and I was honestly hoping I would not be that, because finding someone able to do that properly and at a reasonnable cost here in Mexico will be a nightmare.
If anyone knows of a good shop in Texas, I might do it when traveling.

I'll start with the plugs replacement and the cleanng product to discard the injectors.

[BashShah]

Originally Posted by Fabmex

Thanks for your feedback Dark Nemesis.
I have read a lot lately on that Walnut blast and I was honestly hoping I would not be that, because finding someone able to do that properly and at a reasonnable cost here in Mexico will be a nightmare.
If anyone knows of a good shop in Texas, I might do it when traveling.

I'll start with the plugs replacement and the cleanng product to discard the injectors.

Febmex,
Ok, first try to find an auto tools store that sells this walnut blaster or the shells for it.
Then call that store and see who bought it or even on a regular basis.

Then call them up.

Or look up VW shops, and ask them if they know what walnut blasting is, if they don't call another shop

Then approach that shop.

Just my way I would go about it.
Else.
Make the trip.

DN