E92 Misfire

[mr.naude 0]

Hi guys. I have a problem with my 2006 E92 335i, 150,000kms.
Usually when a problem pops up, i fix it myself (with help from google and forums). Now it has developed a misfire.
It only misfires on low RPM, between idle and 3000. Sometimes i feel it shake and stutter, other times its runs fine.

I get a check engine light, and all scans dictate that the misfire is only in cyl. 5.

Obviously there are a few things to troubleshoot. I have swapped coils, misfire still in cyl. 5.

The plugs were replaced about 6 months ago, so i'm pretty sure its not them.

The 3rd concern was the injector. I have removed it, cleaned the outsides, and stuck it back in.
I have had a chat with a BMW mechanic, and he says its very unlikely that it might be the injector.

So my question is, how/where/what do i check next?

Really want this problem gone. Preferably without spending $1000's.

HELP!

[trottsky 24]

The low pressure fuel sensor and also the high pressure fuel pump can throw up intermittent misfire faults on the n54. It's hard to catch them faulting sometimes via diagnostics as they don't often completely fail. I'm not saying it's definitely that as you're only getting misfires specific to one cylinder, but keep it in the back of your mind, symptoms sound spot on

[mr.naude 0]

Thats exactly what i was thinking, hpfp. But as you say, then the misfires would be across multiple cylinders. Its just on cyl. 5, and as you say, it doesnt always throw a code. It will misfire all day long, for example, then just display one error code. When i clear the code, it will only show again after a few days. But the misfire is still there.

[jake1829 119]

I would change the spark plugs - gone through 2 sets of OEM plugs and on my 3rd set in a year of owning the car.

Tho my car is tuned etc , done about 25k and tracked regularly in that year.

edit**

would also get a walnut blast done to clean your intakes if never done - n54 is notorious for having gunked up intakes

Edited July 17, 2014 by mod335

[RobD 41]

Duff fuel injector. I had the same symptoms on cylinder 6. Plugs were fine. Fuel pump fine. Coil fine. Leaves one likely culprit. Get the injector duty cycle checked on a scanner.

Edited July 17, 2014 by RobD

[mr.naude 0]

Thanks guys. Almost have it completely figured out now. Now I've read a whole lot about replacing injectors. And I get a number of different stories.

1. Can i just replace 1? I know i have to have it coded.

2. Can i just switch 2 injectors around to see if the problem follows? (Just to make sure it is the injector)

3. Have any of you done the coding yourselves? Is it tricky? (I'm quite IT minded)

4. Can I smack the whole injector into an ultrasonic batch to clean it?

5. Who does the wallnut blasting, and at what cost?

[RobD 41]

Yes you can replace just one. I had one replaced by Burgers Motor Works late last year. I had a horrible misfire on cylinder 6. Basically the injector wasn't closing and was therefore overfuelling the cylinder and the mixture wasn't combusting. They can test the open/close cycle on the spot with their diagnostics. They just take it out, replace it, code it and its done.