p0306 code for cylinder misfire and seatbelt extender problem (07 e92 335i)

twistedspoon · 02-11-2015, 02:40 AM

Hopefully this is the right subforum for this. Purchased an 07 E92 335i over the weekend. 114K miles which was a little higher than I wanted but the price was pretty good and last owner (second who bought CPO) seemed like he took care of it.

anyway, I got a "service engine soon" light so I scanned it with my bluetooth OBDII tool and got a P0306 code for engine misfire. I did some research and it seems like spark plugs are generally the solution for this problem.

I cleared the code with the Torque app on my phone and the "service engine soon" light disappeared when the car is on, but it shows up again when I start the engine. is this normal? or should I not worry about this until I get the new spark plugs in (hopefully they come in soon).

the other problem is that the seatbelt extender on both seats doesn't "catch" the seat belt properly, it just slides right by. any suggestions on a fix for that?

hopefully I'm on the right track with the P0306 code. please let me know if anyone has any suggestions.

Phil325i · 02-11-2015, 02:48 AM

This might work for your belt butler...

twistedspoon · 02-11-2015, 11:45 AM

Quote:

Originally Posted by Phil325i

This might work for your belt butler...

i'll take another look at it and see if this is the problem. I don't think it is though, the problems seemed more that the folding part of the arm didn't fold out all the way. I'll take a video later today.

twistedspoon · 02-12-2015, 01:52 AM

didn't get to test the seat belt arm today but I did some research (aka read the service/owners manual).

it seems the car has a built in notification for when the spark plugs need to be replaced. that notification does not show up on my gauges; does this eliminate the spark plugs being the cause behind the p0306 code or is that not the case?

vapore0n · 02-17-2015, 08:06 AM

Does the car stumble a little when starting up and then stabilize itself after a few seconds?

I used to have the P306 code, misfire cyl 6. I replaced sparks and coils. After all of that, I found out the problem was a leaking injector, so I had to replace that too.

You can do proper diagnostics before changing anything out. Swap sparks and plugs from cylinder6 to a different one. See if the error moves to the new cylinder. If it does not, start considering changing the injector.

There seems to be a way to diagnose injectors too. By measuring the voltage through them. Ive just read that in the forum, have never done it.

jon_335 · 02-17-2015, 08:47 AM

I wouldn't rule out the plugs based on the service reminder. It could have been reset at some point without the plugs being changed out. Seems to me that putting in new plugs is a good place to start and if nothing else gives you the peace of mind of knowing how new/old they are.

twistedspoon · 02-18-2015, 11:53 PM

Quote:

Originally Posted by vapore0n

Does the car stumble a little when starting up and then stabilize itself after a few seconds?

I used to have the P306 code, misfire cyl 6. I replaced sparks and coils. After all of that, I found out the problem was a leaking injector, so I had to replace that too.

You can do proper diagnostics before changing anything out. Swap sparks and plugs from cylinder6 to a different one. See if the error moves to the new cylinder. If it does not, start considering changing the injector.

There seems to be a way to diagnose injectors too. By measuring the voltage through them. Ive just read that in the forum, have never done it.

Quote:

Originally Posted by jon_335

I wouldn't rule out the plugs based on the service reminder. It could have been reset at some point without the plugs being changed out. Seems to me that putting in new plugs is a good place to start and if nothing else gives you the peace of mind of knowing how new/old they are.

UPDATE - I changed out all the spark plugs and 1 coil (#6) and cleared the code using Torque. When I started the engine, the SES light was still on and rescanning the ECU continued to give me the P0306 code. The vibrating at 3000 rpms at high speeds has gone away (so it seems like it was a good idea to change the plugs out anyway), but now I'm noticing some very slight, weird shaking/jerking when idling that feels like it's coming from under the seat. Next step is injector? Sounds painful

vapore0n · 02-19-2015, 06:55 AM

Procedure doesnt look painful. But you have to code the new ones in. Id say that is the worst part.(and Im a software engineer)

eblong420 · 07-10-2019, 03:05 PM

Injectors are very easy. Coding is very simple as long as you have programming tool you can use (Snap-On scanners work just fine). Just make sure that you get the latest version of the injectors if you are replacing them all or the same series as the rest of the ones in your car. The series is located after the part number.

02-11-2015, 02:40 AM	#1
twistedspoon Private First Class 158 Rep 151 Posts Drives: 2023 G80 M3 Join Date: Jan 2015 Location: DFW, TX iTrader: (0) Garage List 2007 BMW 335i [0.00]	p0306 code for cylinder misfire and seatbelt extender problem (07 e92 335i) Hopefully this is the right subforum for this. Purchased an 07 E92 335i over the weekend. 114K miles which was a little higher than I wanted but the price was pretty good and last owner (second who bought CPO) seemed like he took care of it. anyway, I got a "service engine soon" light so I scanned it with my bluetooth OBDII tool and got a P0306 code for engine misfire. I did some research and it seems like spark plugs are generally the solution for this problem. I cleared the code with the Torque app on my phone and the "service engine soon" light disappeared when the car is on, but it shows up again when I start the engine. is this normal? or should I not worry about this until I get the new spark plugs in (hopefully they come in soon). the other problem is that the seatbelt extender on both seats doesn't "catch" the seat belt properly, it just slides right by. any suggestions on a fix for that? hopefully I'm on the right track with the P0306 code. please let me know if anyone has any suggestions.
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02-11-2015, 02:48 AM	#2
Phil325i Brigadier General 616 Rep 3,194 Posts Drives: E92 325i MSport Coupe Join Date: Apr 2012 Location: UK South East iTrader: (1) Garage List 2009 BMW 325i Coupe [6.00]	This might work for your belt butler... __________________ E92 pre-LCI 325i - Ohlins R&T; H&R spacers; M3 strut brace; Swift thrust sheets; 3 x chassis braces; diff brace; N53 V-brace; 034 subframe inserts; BMS clutch stop; BMS CDV; RE g/box mounts; Delrin shift bushes; Saikoumichi OCC; Cyba scoops; BMW Perf Exhaust; HEL s/steel brake hoses; M3 rear spoiler; Recaro Sportster CSs; M3 white dash LEDs; LED Angels; LED side repeaters; BMW Perf black grille; CSL reps; SSDD carbon diffuser; Monster Wrap black roof/clear front
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02-12-2015, 01:52 AM	#4
twistedspoon Private First Class 158 Rep 151 Posts Drives: 2023 G80 M3 Join Date: Jan 2015 Location: DFW, TX iTrader: (0) Garage List 2007 BMW 335i [0.00]	didn't get to test the seat belt arm today but I did some research (aka read the service/owners manual). it seems the car has a built in notification for when the spark plugs need to be replaced. that notification does not show up on my gauges; does this eliminate the spark plugs being the cause behind the p0306 code or is that not the case?
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02-17-2015, 08:06 AM	#5
vapore0n Captain 40 Rep 669 Posts Drives: 2010 335i Join Date: Jul 2011 Location: MA iTrader: (0)	Does the car stumble a little when starting up and then stabilize itself after a few seconds? I used to have the P306 code, misfire cyl 6. I replaced sparks and coils. After all of that, I found out the problem was a leaking injector, so I had to replace that too. You can do proper diagnostics before changing anything out. Swap sparks and plugs from cylinder6 to a different one. See if the error moves to the new cylinder. If it does not, start considering changing the injector. There seems to be a way to diagnose injectors too. By measuring the voltage through them. Ive just read that in the forum, have never done it.
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02-17-2015, 08:47 AM	#6
jon_335 Second Lieutenant 15 Rep 276 Posts Drives: 2007 BMW 335i Join Date: Feb 2013 Location: North Carolina iTrader: (1)	I wouldn't rule out the plugs based on the service reminder. It could have been reset at some point without the plugs being changed out. Seems to me that putting in new plugs is a good place to start and if nothing else gives you the peace of mind of knowing how new/old they are. __________________ 2007 BMW 335i \| Garner, North Carolina
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02-19-2015, 06:55 AM	#8
vapore0n Captain 40 Rep 669 Posts Drives: 2010 335i Join Date: Jul 2011 Location: MA iTrader: (0)	Procedure doesnt look painful. But you have to code the new ones in. Id say that is the worst part.(and Im a software engineer)
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07-10-2019, 03:05 PM	#9
eblong420 Registered 0 Rep 1 Posts Drives: e90 n54 2009 Join Date: Jul 2019 Location: PA iTrader: (0)	Injectors are very easy. Coding is very simple as long as you have programming tool you can use (Snap-On scanners work just fine). Just make sure that you get the latest version of the injectors if you are replacing them all or the same series as the rest of the ones in your car. The series is located after the part number.
	Appreciate 0 Quote