Strange Misfire Issue with Coil Packs

Ketplunk · 08-17-2020, 04:10 AM

Hi,

So I recently had misfiring when the car was warm and was diagnosed to be a faulty coil pack - garage put in a used one, but told me that they could go at any time. Car was fine with the 'new' one, but I ordered 4 new coil packs (Bosch, I know there are updated Delphi ones, but the Bosch were all I could get my hands on relatively quick).

Coil packs arrived and I replaced them. My old ones seem to have been the updated Delphi packs. I put the 4 new ones in and when I turned the car on it was misfiring severely. Checked the codes, which said there was a misfire in cylinder 3. I assumed it might be a faulty coil so I swapped the coils from two cylinders and tried again. Unfortunately, the code didn't move from cylinder 3. Out of curiosity, I stuck one of the old coil packs back into cylinder 3. And the car ran fine, no misfires? Which I just can't understand.

So basically, 3 cylinders run fine with the new Bosch coils, while one cylinder will misfire with the new ones but runs fine with one of the old coils. Does anyone have any idea what this could be? Just to note the car has had timing chain and injectors done in the last few months, so they could presumably be ruled out. Thanks!

e91Owner · 08-17-2020, 08:49 PM

Are there any other associated codes?

Ketplunk · 08-19-2020, 04:00 AM

Quote:

Originally Posted by e91Owner

Are there any other associated codes?

Nope, just for a misfire detected in that cylinder.

Steve Sas · 08-20-2020, 04:46 AM

usually when this happens its the spark plug gap which is too large.
Seems older coil packs putting out more voltage or new coil pack is faulty.
Did you try one of the other new ignition coils on cylinder 3?

Ketplunk · 08-20-2020, 06:10 AM

Quote:

Originally Posted by Steve Sas

usually when this happens its the spark plug gap which is too large.
Seems older coil packs putting out more voltage or new coil pack is faulty.
Did you try one of the other new ignition coils on cylinder 3?

Spark plugs should only be about 6 months old, but that's something I might look at! Yeah, I swapped the new ignition coils from cylinders that were running fine to cylinder 3 and it still misfired. And the first new coil I put into cylinder 3 works fine in the others, so it doesn't seem to be a faulty coil pack (I think).

Steve Sas · 08-21-2020, 06:06 AM

If you have a spare spark plug, even old one, replace it and see what happens.
And set correct gap.

08-17-2020, 04:10 AM	#1
Ketplunk Registered 0 Rep 3 Posts Drives: BMW 320i E90 Join Date: Aug 2020 Location: Dublin, Ireland iTrader: (0)	Strange Misfire Issue with Coil Packs - 320i N43 Hi, So I recently had misfiring when the car was warm and was diagnosed to be a faulty coil pack - garage put in a used one, but told me that they could go at any time. Car was fine with the 'new' one, but I ordered 4 new coil packs (Bosch, I know there are updated Delphi ones, but the Bosch were all I could get my hands on relatively quick). Coil packs arrived and I replaced them. My old ones seem to have been the updated Delphi packs. I put the 4 new ones in and when I turned the car on it was misfiring severely. Checked the codes, which said there was a misfire in cylinder 3. I assumed it might be a faulty coil so I swapped the coils from two cylinders and tried again. Unfortunately, the code didn't move from cylinder 3. Out of curiosity, I stuck one of the old coil packs back into cylinder 3. And the car ran fine, no misfires? Which I just can't understand. So basically, 3 cylinders run fine with the new Bosch coils, while one cylinder will misfire with the new ones but runs fine with one of the old coils. Does anyone have any idea what this could be? Just to note the car has had timing chain and injectors done in the last few months, so they could presumably be ruled out. Thanks!
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08-17-2020, 08:49 PM	#2
e91Owner e91Owner 425 Rep 1,129 Posts Drives: 2011 e91 & 2010 e60 Join Date: Mar 2018 Location: Out of the Office iTrader: (0)	Are there any other associated codes?
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08-20-2020, 04:46 AM	#4
Steve Sas Private First Class 24 Rep 144 Posts Drives: BMW 335i 2008 Join Date: May 2020 Location: Sydney iTrader: (0)	usually when this happens its the spark plug gap which is too large. Seems older coil packs putting out more voltage or new coil pack is faulty. Did you try one of the other new ignition coils on cylinder 3?
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08-21-2020, 06:06 AM	#6
Steve Sas Private First Class 24 Rep 144 Posts Drives: BMW 335i 2008 Join Date: May 2020 Location: Sydney iTrader: (0)	If you have a spare spark plug, even old one, replace it and see what happens. And set correct gap.
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