Cold weather start up misfires

Reaper0995

Specialist
Jan 10, 2017
69
20
0
im having troubleshooting misfires no my car. 2008 335xi, 104k miles, FBO. When it is about 40 degrees or colder out, my car starts up like normal and within a minute starts hesitating and throwing a check engine light. When I check the MHD serval codes come up to say multiple misfires, or misfires on cylinders 4/5/6. More often, cylinder 6 will keep throwing a code a few more times. Obviously the car runs very rough until I clear the codes. Sometimes only need to do it once, sometimes five or six times.


Reading around it looks like a ton of problems could cause this, which is annoying... I tried swapping the front and rear plugs, 1-6,2-5,3-4 but the misfires did not follow the plugs. I swapped the front wideband sensors, couldn't swap the rears because the plugs are not interchangeable, and no change. I checked all six plugs and all but cylinder one look the same. Cylinder one looks to have an injector that is leaking and wetting the plug, another issue for another day. I cleaned and reinstalled the vanos solenoids, no change either. I have tried going back and forth from a more aggressive tune to stock, back and forth and no change. Also tried to tighten all downpipes connections.


So I tried coils, vanos, front widebands, looked at plugs, changes tune to stock, tighten for exhaust leaks, and nothing... looking around several other things look like they may cause this; PCV valve, valve cover, exhaust leak I didn't find, replace wideband sensors, new vanos solenoids, adjust downpipes fix thing, new coils, new plugs, new injectors, new hpfp...? That is a huge list of pricey parts to randomly fix without nkowing kit will even fix the issue!

Please help!
 

doublespaces

General of the Army
Oct 18, 2016
8,940
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AZ
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2009 E93 335i
What kind of fuel are you running? If it starts fine, then perhaps that may not be the problem.
 

R.G.

Lieutenant
Nov 17, 2016
669
325
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Henderson, NV
Ride
E92 335, F10 M5
Typically cold starts issues and E content in fuel go hand in hand


Sounds stupid simple but try this. Some DME's that weren't software updated don't do this on their own from what I remember. Get in the car, turn ignition on and leave engine off for 10 seconds, then turn it over. Allows the lpfp to prime. Updated DME's do that as soon as it wakes up
 

Reaper0995

Specialist
Jan 10, 2017
69
20
0
Regular pump gas, I'm in Colorado so it's 91 winter blend.

The downpipes fix thing is the little electrical device that plug some into the DME after the cats are removed from new downpipes. I installed it last October and drove throug the winter with no issues, so I don't think this is it since it would have had issues last winter. But I do believe I've seen someone blame this issue no it...
 

Reaper0995

Specialist
Jan 10, 2017
69
20
0
Typically cold starts issues and E content in fuel go hand in hand


Sounds stupid simple but try this. Some DME's that weren't software updated don't do this on their own from what I remember. Get in the car, turn ignition on and leave engine off for 10 seconds, then turn it over. Allows the lpfp to prime. Updated DME's do that as soon as it wakes up


I think mine is updated, when I unlock the car I can hear the lpfp pumping for a second to prime the system. I will try this though.

Also forgot to mention that I have reset most if not all the adaptations at least once, and no changes. Did this on the tune and reset again when back to stock tune was loaded.
 

Euro venom

Specialist
Nov 5, 2016
95
94
0
Tualatin, or
I had this issue last winter and found out it was my injectors leaking. My car would also misfire doing 60mph @ 2k rpms, Which my Tech told me is one of the symptoms.
 

colo_evo

Corporal
Jun 6, 2017
151
108
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E90 335i MT
I had this issue last winter and found out it was my injectors leaking. My car would also misfire doing 60mph @ 2k rpms, Which my Tech told me is one of the symptoms.

Would this throw a cel at 60mph, or could you just feel it?
 

Reaper0995

Specialist
Jan 10, 2017
69
20
0
I can swap them around this weekend. Of thing is injector 1 is the obvious leaker, but cylinder 6 seems to be the misfire... cylinder one is the front cylinder, correct? And cylinder six is to the firewall? The front injector is the leaker.
 

Bmwfixerguy1

Lieutenant
Jun 5, 2017
873
288
0
Ride
07 335i MT
Cold start misfires are almost always injectors. Let vehicle sit cold.
Start and let run for about 45 seconds.

Shut it down and pull plugs, look for your soaked plug and that's your bad injector
 
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dyezak

Major
May 4, 2017
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Plano TX
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335is
Cold start misfires are almost always injectors. Let vehicle sit cold.
Start and let run for about 45 seconds.

Shut it down and pull plugs, look for your soaked plug and that's your bad injector

Agreed, this is the way to find the bad injector.

Unless it's so bad it's throwing misfire codes. Then the DME tells you what injector is the problem child.
 

Reaper0995

Specialist
Jan 10, 2017
69
20
0
just to clarify when you say cold start the engine, do you mean after it sits overnight? Or when it's literally cold outside? I can definitely do this this weekend if it's just after sitting overnight. May not get weather cold for a few days though.
 

Reaper0995

Specialist
Jan 10, 2017
69
20
0
Thanks again to everyone for the support, been hunting this down for a while and just can't solve this!
 

Bmwfixerguy1

Lieutenant
Jun 5, 2017
873
288
0
Ride
07 335i MT
just to clarify when you say cold start the engine, do you mean after it sits overnight? Or when it's literally cold outside? I can definitely do this this weekend if it's just after sitting overnight. May not get weather cold for a few days though.
Your best bet is just letting it sit overnight. Then doing what I described. 60 or 20 deg out won't really make a great difference for what you want to find out.
It can be more noticeable to you when colder that's all