Intermittent startup issue and cylinder number five misfire?

Tiny
BIGBORG
  • MEMBER
  • 2004 BMW 645
  • 4.4L
  • V8
  • 2WD
  • AUTOMATIC
  • 67,500 MILES
Startup Issue:

For a while, the car has been doing what I can only describe as a choked/hesitant startup. Typically, when the car is warming up or warmed up, sometimes from cold start.

I have 2 minor vacuume leaks confirmed by a garage, from the exhaust cam position sensor gasket/seals on bank #1 and #2, but the garage said they don't think that would be the cause.

Thinking logically, I had a code: 00272C - DME: Additive mixture adaptation, bank 1 & bank 2- control limit reached.
In my mind, vac leak would be affecting the fuel to air ratio and possibly causing this?


Misfire Issue:

I had a misfire logged in cylinder #5 about 2 months ago. As far as I can tell, they all have NGK plugs, but I replaced #5 with a Bosch and also replaced the ignition coil with a new Bosch one. This fixed it for about a month and now the misfire has come back in the same cylinder.

From my own research, Bosch plugs are sometimes questionable, and that NGK are the spark plugs to use, but you can't believe everything you read on the internet.
Could this possibly be causing the misfire?

Additionally, would the vac leak mentioned above be causing a misfire?
I'm unsure on that as you'd think it wouldn't only be affecting one particular cylinder.


Any help and advice would be greatly appreciated

Many thanks
Monday, February 3rd, 2025 AT 9:54 PM

3 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 49,440 POSTS
Yep, I agree, I would replace the spark plug again and be careful not to crack it. Next, I would do a com pression test and if okay replace the fuel injector, this can cause the codes you have, please clear them after the repair. Here are two guides to help and I have included how to change the fuel injector out as well.

https://www.2carpros.com/articles/how-to-test-engine-compression

and please go over this guide as well:

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

Check out the images (below). Please upload pictures or videos in your response of any problems so we can see what to help you with.
Was this
answer
helpful?
Yes
No
Tuesday, February 4th, 2025 AT 11:04 AM
Tiny
BIGBORG
  • MEMBER
  • 2 POSTS
Thanks for the reply.

I've replaced #5 plug, and it seemed to be good for a couple of days. However, I went to test last night and had a misfire in #5 once again after a cold start. I turned the car off and let it sit for a minute or two, then turned it back on again.
Weirdly enough, the misfire went away, I went for a hard drive and the car doesn't seem down on power or feel lumpy, so it seems to be an intermittent misfire.

I haven't had a chance to check the other stuff mentioned, but any ideas as to why it happened once and then went?

Thanks
Was this
answer
helpful?
Yes
No
Friday, February 7th, 2025 AT 6:27 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 49,440 POSTS
The fuel injector can come and go, but can I ask if you replaced the ignition coil for that cylinder?
Was this
answer
helpful?
Yes
No
Friday, February 7th, 2025 AT 6:11 PM

Please login or register to post a reply.

Sponsored links