[Jeff@TopGearSolutions]

All First Time Tuners to this platform should read this sticky. This car has a history of misfires and they are all well documented and typically easy to fix. If you are new to tuning your vehicle and you have over 25,000 miles on your vehicle spark plugs the first thing you should do before installing your tune is get fresh spark plugs. This problem is so common for newly tuned vehicles that even Cobb has made a video.

Cobb's Video on Misfires
http://www.youtube.com/watch?feature...&v=FsNK1ySAlSo

Here is a list of things you can try in no particular order and there may be more. I would suggest starting with the least expensive ideas first.

-Spark Plug Gap
- New Spark plugs
- Swapping Coilpacks
-New Coilpacks
-Injectors
-High Pressure/Low Pressure Fuel Pump
-Carbon Build up in intake valves
-Vanos Solenoid

Troubleshooting Misfires

Multiple cylinders Misfires:

Check Your Spark Plug Gap *Free Fix* :
The cheapest quick fix is to ensure your spark plug gap is within spec. BMW 135i and BMW 335i Stock Spark Plug gap for 2007-2010 is .028".

Replace Spark Plugs:
Buy a new set of OEM Bosch plugs from the dealer or aftermarket NGK 5992. The NGK will need to be re-gapped and historically do not last as long as the OEM Bosch but are cheaper. Spark plugs should be changed every 25,000 miles (Bosch) or 10,000-15000 Mile (NGK).

Single Cylinder Misfire

Swap Coil Packs :
Try swapping coil packs to see if the problem moves to another cylinder: i.e. if cylinder 1 is misfiring, swap coil 1 to 3 and see if the misfire now happens on cylinder 3. If it moves the coil pack needs replacement.

If the misfires does not move then you need to check your spark plug gap and or replace them before moving on to the next steps.


If changing spark plugs and moving/replacing coil packs does not work it could be the following:


Leaky Injector: Your spark plug(s) would show an indication of fouling and smell of fuel. This would be an indication your injectors may be leaking at the seals. A leaky injector in most cases also causes a rough start and or idle.

Weak/ Failing Low Pressure Fuel Pump: Not as common but a weak LPFP can cause misfires. You can measure this by trying to get logs from your tune of the LPFP voltage/pressure. You can also check your fuel trims to see if they are exceeding 31-34%. (However, your tune may just need adjustment). We advise to contact your tuner of choice in regads to fuel trims and if your low pressure pump may be on the fritz.

Weak/Failing High Pressure Fuel Pump: Not as common but a weak HPFP can also cause misfires.

Excessive Carbon on Intake Valves: This will happen to all N54 Engines. It is a result of not having fuel sprayed over the intake valves like traditional Port Fuel Injection. Since the N54 is direct injection over time the intake valves gunk up with carbon deposits. We've seen historically that after 35,000 miles all N54 vehicles could use a Intake Valve Cleaning. The benefits for most are smoother power delivery, increased power, smooth idle and in some cases a fix for misfires.

Vanos Solenoids: Usually attributed with Vanos codes, the Vanos Solenoids can cause misfires. A quick fix is to clean them. See DIY.

[import36]

sticky?!

[JamesM3M5]

Yes, STICKY THIS THREAD. It's a little more "politically correct" than the previous thread a couple months back entitled "Change your damn plugs... stop wasting forum space..."

But yeah, this is long overdue. Thanks, Jeff!

[cyniclaus]

Thanks, I changed my plugs at 45k and it seemed to solve my problems. I've got about 8k on AP Stage 1

Is there a recommended mileage to change the coilpacks or a vertain mileage where they typically start to go?

What about carbon cleaning? At what mileage should we get cleaned and can any mechanic do it or should it be a BMW specialist? Can/will the dealer perform that?

Are the coilpacks or carbon covered under the CPO warranty or is that considered normal wear like brakes or the clutch?

[vasillalov]

So basically, what you are saying that after eliminating the obvious: spark plugs and coils, it could be a wide variety of things that can cause a misfire: anything from carbon build up, bad fuel injector, fuel pump , etc etc.

...not the moon phase?

What do you suggest for my situation:

* 25K miles on car
* Brand new spark plugs
* Swapping coils does not move the misfires to a different cylinder
* Injectors and HPFP replaced less than 5K miles during recall campaign

[GeorgiaTech335coupe]

I think injectors should get their own step, after spark plugs and coils. In my case I have had more injectors go out than bad plugs and bad coils combined. Plus they are the 3rd cheapest step before LPFP, HPFP, and carbon buildup cleaning.

[JamesM3M5]

Carbon cleaning should run $800-1000. Not particularly cheap, but not too steep, either. It should be done every 30-40k miles at least. I bought mine with 46k, did the cleaning at 47k, and the buildup was horrendous. I noticed much smoother running and a little better power at the top end. I manually scrubbed with gun cleaning brushes and carb cleaner. Forget that! It was a mess and a PITA. I bought the BMW walnut shell blasting tool to do Mini and BMW DI engines. Maybe I'll run a special on cleaning services next month...

Wow, I didn't know injector prices had come down that far: 13 53 7 585 261 is $135 retail, available from Tischer BMW for $108 (20% off retail) each.

Vas, try replacing the coils - all of them. If they don't fix it, you're not out a whole lot. 12 13 7 594 937 $60 retail, $48 from Tischer.

[GeorgiaTech335coupe]

Originally Posted by JamesM3M5

Carbon cleaning should run $800-1000. Not particularly cheap, but not too steep, either. It should be done every 30-40k miles at least. I bought mine with 46k, did the cleaning at 47k, and the buildup was horrendous. I noticed much smoother running and a little better power at the top end. I manually scrubbed with gun cleaning brushes and carb cleaner. Forget that! It was a mess and a PITA. I bought the BMW walnut shell blasting tool to do Mini and BMW DI engines. Maybe I'll run a special on cleaning services next month...

Wow, I didn't know injector prices had come down that far: 13 53 7 585 261 is $135 retail, available from Tischer BMW for $108 (20% off retail) each.

Vas, try replacing the coils - all of them. If they don't fix it, you're not out a whole lot. 12 13 7 594 937 $60 retail, $48 from Tischer.

Best coil prices are found here. Free shipping if your order is over $50, so order a spare.

http://www.bimmerpartswholesale.com/...921+4294967171

[vasillalov]

Originally Posted by JamesM3M5

Wow, I didn't know injector prices had come down that far: 13 53 7 585 261 is $135 retail, available from Tischer BMW for $108 (20% off retail) each.

Yep. Bought one to replace it on cyl1, hoping that it will cure the problem. I suspect this injector was not calibrated correctly into the ECU, but I will know more once I get my INPA cable.

Originally Posted by JamesM3M5

Vas, try replacing the coils - all of them. If they don't fix it, you're not out a whole lot. 12 13 7 594 937 $60 retail, $48 from Tischer.

6 new coils at just 25K miles?! That's rather illogical. If the injector replacement does not cure it, I will try maybe 1 new coil.

The one thing I hate the most is throwing money on parts and blindly hoping it will fix a problem!

[vasillalov]

What I'd like to know is this:

OEM specifications for electrical resistance of the coils. One could easily do a home test with a mid-range volt meter.

[JamesM3M5]

Originally Posted by vasillalov

What I'd like to know is this:

OEM specifications for electrical resistance of the coils. One could easily do a home test with a mid-range volt meter.

hotrod posted a thread on this a few weeks back. He checked his used coils versus new ones. I don't think they solved his misfire, but he did solve it in that thread.

Resistance doesn't tell us enough about the behaviour of the coil under load. It's useful to check, but probably isn't the end-all of the coil diagnosis.

I agree on not throwing parts at a problem - wastes time and money. But you can easily sell the set to anyone here on the forums. Any track or drag race enthusiast should have a spare set whenever they go to a track event.

[landman2k1]

When I installed my JB4 a few months back I was getting a misfire on cylinder 1, swapped the 1/2 coil and the misfire jumped to cylinder 3. Strange! Just got around to changing plugs and all seems to be well. 40K miles, so it was probably time anyway.

[blisstik]

Don't forget about resetting your adaptations! It should be one of the first things you try out before swapping any parts. This is helpful if you feel that your car is starting to bog in the low RPMs. I know it worked for me.

http://www.e90post.com/forums/showthread.php?t=386376

[vasillalov]

Originally Posted by blisstik

Don't forget about resetting your adaptations! It should be one of the first things you try out before swapping any parts. This is helpful if you feel that your car is starting to bog in the low RPMs. I know it worked for me.

http://www.e90post.com/forums/showthread.php?t=386376

I have an email from Rob from Cobb in which he specifically recommends NOT to reset adaptations because boost will get choppy.

[zeel]

Originally Posted by JamesM3M5

Carbon cleaning should run $800-1000. Not particularly cheap, but not too steep, either. It should be done every 30-40k miles at least. I bought mine with 46k, did the cleaning at 47k, and the buildup was horrendous. I noticed much smoother running and a little better power at the top end. I manually scrubbed with gun cleaning brushes and carb cleaner. Forget that! It was a mess and a PITA. I bought the BMW walnut shell blasting tool to do Mini and BMW DI engines. Maybe I'll run a special on cleaning services next month...

Wow, I didn't know injector prices had come down that far: 13 53 7 585 261 is $135 retail, available from Tischer BMW for $108 (20% off retail) each.

Vas, try replacing the coils - all of them. If they don't fix it, you're not out a whole lot. 12 13 7 594 937 $60 retail, $48 from Tischer.

If you decide to run a special on cleaning services for carbon buildup, please post it in the mid-atlantic forum. I'm definitely looking into this in the next month or so.

[Mike@N54Tuning.com]

When tuned plugs should be replaced every 15-20K. Will solve a lot of headaches and its cheap to do if you can DIY. Just grab a spark plug socket and order some plugs and go for it. Your car will thank you.

Mike

[nitehawk]

Originally Posted by vasillalov

I have an email from Rob from Cobb in which he specifically recommends NOT to reset adaptations because boost will get choppy.

Care to share? Wouldn't that just be a temporary symptom until the DME relearns each adaptation?

[vasillalov]

Originally Posted by nitehawk

Care to share? Wouldn't that just be a temporary symptom until the DME relearns each adaptation?

Sure:

from: Irish rob.irish@cobbtuning.com
to: Vasil Lalov <vasil.lalov@gmail.com>
date: Tue, Dec 20, 2011 at 12:37 PM
subject: Re: Stage 2+FMIC - Misfires
mailed-by: cobbtuning.com
: Important mainly because of your interaction with messages in the conversation.

Hi Vasil,

Please see the attached map to see if we can get your misfires under control. Let me know how it works.

The boost control should smooth out over time. Resetting the learning would delay it.

Cheers,
Rob

I agree. The ECU will eventually re-learn new adaptations.

BTW, that map he gave me only made things worse. I am not saying anything else till I get my new injector in the mail. I am also waiting on an INPA cable so that I can do my own coding, Local stealership wants $160 for recoding. Local indy shop wants $90 for recoding a single injector. Pffft!

[Jeff@TopGearSolutions]

I updated first post with a little more info.

If you guys think I should add something specific just shoot me a PM with "misfire code thread" in subject line.

[SlowerThanU]

For heavy meth users (that sounds bad), O2 sensors should be on the list
For high HP cars, compression/leak own should be checked

[chesney72]

Not sure if this is a fix but I think it helps. If you take the coils out and clean the contact point of the residue that can build up on them it will give the coil a better chance to get a clean contact with the spark plug.

I've been missfire free since doing this....touch wood!!

[mundo74]

Originally Posted by vasillalov

Sure:



I agree. The ECU will eventually re-learn new adaptations.

BTW, that map he gave me only made things worse. I am not saying anything else till I get my new injector in the mail. I am also waiting on an INPA cable so that I can do my own coding, Local stealership wants $160 for recoding. Local indy shop wants $90 for recoding a single injector. Pffft!

Tell us a bit more about this inpa cable. Was hoping bav technic added this to their cable