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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > NA Engine (non-turbo) / Drivetrain / Exhaust Modifications > P306 Misfire Code, Need new plugs? Coil?



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      04-03-2011, 06:15 PM   #1
bmwstylexx
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P306 Misfire Code, Need new plugs? Coil?

Took the car to Autozone and they scanned the CEL for me and showed P306 - engine misfire.. Said I might need new plugs and coil? But they didn't have the plugs I needed so I went to Advance and they said the coil was cyclinder specific and I would need to know which one I needed? So now I'm confused...

How do I know which coil I need replaced (of if i even need a coil replaced)? Car had a slow crank, now CEL is on and car "Shakes" when started.

Any help would be appreciated.
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      04-03-2011, 06:29 PM   #2
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I had the same code, it was an ignition coil, it was about $250 at the dealer. I think the part was $70. I will DIY if it ever happens again for sure
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      04-03-2011, 06:42 PM   #3
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Originally Posted by arctic330i View Post
I had the same code, it was an ignition coil, it was about $250 at the dealer. I think the part was $70. I will DIY if it ever happens again for sure
That's what they thought it was as well... The code says "Misfire on Cyclinder 6"... Which cyclinder is 6? the first one at the front? or the last one at the back? (see pic) They said if i switch the coil from cyclinder 6 to cyclinder 5 and it was the cyclinder that was faulty.. the new code would now say "Misfire cyclinder 5.. instead of Misfire cyclinder 6"
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      04-03-2011, 11:08 PM   #4
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anyone know which way the cyclinders are numbered????
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      04-03-2011, 11:09 PM   #5
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No your cylinders arent in that order, have your car running and pull each coil out 1 by 1..Basically take the first one out and if it sounds like its gonna stall or losses power or sounds funny then you know the coil is working, put it back in and move onto the next coil.. When you pull the coil and no change is made , then that is the faulty coil.. Depending on how bad and how long you been riding your car like this, your plugs might be fouled from all the unburnt fuel but you should be ok with spark plugs. And it shouldnt matter which cylinder it is cuz all the coils do the same shit .. Just bring in the coil pack that is bad and tell them you need that part. Its not like your changing out your piston rings or checking compression ratio to know exactly which cylinder is what. GL
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      04-03-2011, 11:12 PM   #6
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Quote:
Originally Posted by Got Euro ? View Post
No your cylinders arent in that order, have your car running and pull each coil out 1 by 1..Basically take the first one out and if it sounds like its gonna stall or losses power or sounds funny then you know the coil is working, put it back in and move onto the next coil.. When you pull the coil and no change is made , then that is the faulty coil.. Depending on how bad and how long you been riding your car like this, your plugs might be fouled from all the unburnt fuel but you should be ok with spark plugs. And it shouldnt matter which cylinder it is cuz all the coils do the same shit .. Just bring in the coil pack that is bad and tell them you need that part.
If the car is already "shaking" and making a rough idle noise will this process work?
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      04-03-2011, 11:15 PM   #7
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Yes....... Just go 1 by 1, trust me lol you will know which one is bad.
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      04-03-2011, 11:18 PM   #8
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Originally Posted by Got Euro ? View Post
Yes....... Just go 1 by 1, trust me lol you will know which one is bad.
Alright. Thanks! Ill try this tomorrow.
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      04-04-2011, 08:28 AM   #9
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Quote:
Originally Posted by bmwstylexx View Post
That's what they thought it was as well... The code says "Misfire on Cyclinder 6"... Which cyclinder is 6? the first one at the front? or the last one at the back? (see pic) They said if i switch the coil from cyclinder 6 to cyclinder 5 and it was the cyclinder that was faulty.. the new code would now say "Misfire cyclinder 5.. instead of Misfire cyclinder 6"
The position of the coils is:

[Back] 6 - 5 - 4 - 3 - 2 -1 [Front]

It's most likely a bad coil, if you need to replace the coils, it's good to replace all 6 as if one fails, the others are probably right behind it. It's about $40 a coil from Tischer BMW, you can order your spark plugs from them too and swap out the plugs while you are at it.
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      04-04-2011, 10:16 AM   #10
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You should find someone with an Autologic, BT tool, GT1 etc and pull the codes.....it will tell you which cylinder is misfiring.
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      04-04-2011, 10:28 AM   #11
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Quote:
Originally Posted by ********* View Post
You should find someone with an Autologic, BT tool, GT1 etc and pull the codes.....it will tell you which cylinder is misfiring.
For a misfire code, a standard OBDII scanner is fine. P306 is misfire in cylinder 6. Just needs to swap the coils of 5 and 6, clear the code, start up the car and see if a code comes up in cylinder 5 (should be P305), if so, bad coil. Replace dead coil, clear code, enjoy.
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      04-04-2011, 11:09 PM   #12
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Quote:
Originally Posted by Dracon View Post
The position of the coils is:

[Back] 6 - 5 - 4 - 3 - 2 -1 [Front]

It's most likely a bad coil, if you need to replace the coils, it's good to replace all 6 as if one fails, the others are probably right behind it. It's about $40 a coil from Tischer BMW, you can order your spark plugs from them too and swap out the plugs while you are at it.
Thanks, I changed the plugs out today... was simple to do until I got to plug 6 and that one was a beast being way in the back..

I swapped the coils and had autozone rescan it and sure enough... showed misfire in a different cyclinder, this time cylinder 4. Ordered a replacement from them for $28.. will be here by 10 in the morning... I'm hoping this takes care of it.

Thanks for the info.. at least I know which one 4 is now!
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      04-05-2011, 12:38 AM   #13
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I have a similar problem (P0303) and tried the swap solution on both the coil and the plugs, one at a time, of course. No joy however. The engine still runs like junk.

Does anybody know if the N52 engine has a timing belt or is it a chain? Right now my Volvo 240 engine runs smoother.........
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      04-05-2011, 02:31 AM   #14
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      04-05-2011, 08:07 AM   #15
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This may seem like speculation but is it possible for the cam shaft to slip out of sync by a tooth due to the VVT and not the chain? If so, how do I even check this? I have an OBD scanner but it doesn't show any code beyond the P0303.
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      04-05-2011, 08:52 AM   #16
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you would throw a VANOS code if that happened. Jumping teeth is a much larger problem than misfiring. You do NOT have that issue. (it would happen on ALL cylinders if you jumped a tooth....)
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      04-05-2011, 09:11 AM   #17
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Thanks for this. Perhaps you can suggest a possible fix? The problem occured after I stalled out climbing a hill. (Too slow & wrong gear) I had to jam on the brakes to stop from rolling backwards and do an on hill restart.

Currently, it starts fine but idles and runs rough and has the P0303 code, and lacks power due to running on 5 of 6 cylinders. I am loathe to drive it due to possible engine damage.

The issue seems to be beyond the plug and coil in my case but I am not sure how to proceed beyond checking the compression. I am a newbie to BMWs and am waiting for documentation on the engine.......
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      04-07-2011, 09:52 PM   #18
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Replaced the Coil.... Car runs fine now. Thanks for the info guys.
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      04-07-2011, 10:46 PM   #19
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Quote:
Originally Posted by bmwstylexx View Post
Replaced the Coil.... Car runs fine now. Thanks for the info guys.
Might want to consider replacing the rest if you only replaced one. Once one dies, the others are usually right behind it.
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      04-10-2011, 11:02 PM   #20
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Quote:
Originally Posted by Dracon View Post
Might want to consider replacing the rest if you only replaced one. Once one dies, the others are usually right behind it.
Car is off to Carmax to be sold.... so i just need it to run long enough to get there. lol
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      05-31-2012, 10:28 PM   #21
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Engine coil Miss fire

It was the engine coil in cylinder #5. Got a new coil from O'riellys with life time warrenty.
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