[Ranger Hoopy]

Thank you e90post.
I'm writing my first thread but this community has been a great deal of help to me already while lurking.

I have a stock 2006 330xi that I am trying to keep on the road. My finances are restricted as I am out of work, but even if I wanted to sell this car I need to fix my current issue.

BACK STORY
About 6 weeks ago I started getting misses on cylinder one, my BMW specialist swapped coils and confirmed #1 was bad and #2 was on the brink. They suggested replacing all six, at a cost I won't bother repeating. While they had the car I had been researching here and decided I could insert new coils and put the cover back on the engine as well as they could. (As it turns out I couldn't do it "as well" but that's another story. I replaced #1 and #2, did a full drive cycle to clear all codes and went about my business.

This week I came back from the holidays after 10 days of not starting the car, and it barely started and had terrible power. I put the OBD2 tester in and came up with a persistent misfire on cylinder 5. It seemed reasonable that all the original coils would fail in the same timeframe so I prepared myself to replace #5 and #6 as well, since they are both tough to reach.

But when I swapped #5 with one of the brand new coils, the misfire continued in cylinder 5. Shoot. Well, probably the spark plug, and those are cheap so I'll just replace all 6 regardless. I replaced the plug in cylinder #5, and immediately tested. Engine still ran rough, but the fault code now reports a misfire in cylinder 4. I decided to finish replacing the other 5 plugs, and retest. Still rough, still misfire in #4. Okay, that brings us current.

So what I've read here says for misfire problems start by checking coils, then plugs, then injectors. E90post has got me this far, and I'm grateful. But as a noob who was never dug this deep into an engine bay until now, I'm really confused about injectors. What I've been able to read so far seems to be strictly based on performance-tuned engines, where mine is purely stock. So there's a lot of jargon that I don't understand and I don't know what's applicable. So I'm getting frustrated.

Someone, please tell me to RTFM, but if you could point out the relevant section to me, it would be very helpful. What should I do now to finish troubleshooting this problem?

[PichaDis11]

Lol@ you finding info about misfires in the manual. Well technically they do say to visit your nearest dealership but that's not why we're here.

Ok so now you are at a misfire on cylinder 4. great so I'd repeat the coil swap scenario to rule out the misfire again to see if the misfire follows the coil. Next up is if the plugs are torqued to the correct spec and are the codes being cleared after each repair. IMO

I really do hope that it is not an injector problem.

[Ranger Hoopy]

Thanks for the reply.

I was taking the idea of "the manual" rather loosely, thinking someone might point me to a sticky or a guide or some thread that I should have already looked at! it seems like every time I see injector mentioned, it's in context of turbo engines and custom tuning and programming, none of which I know anything about. At this stage I just want my car to go.

I am reasonably confident that the torque on my plugs is good (it's at least consistent, but I don't have any means of calibrating the torque wrench that I'm using, so I'll have to rely on that, and assume that they're in the ballpark).

I'm now getting multiple misfires, on 2 and 4, and the car really isn't drivable. I think we're at the injector stage, but I've never done injectors, and without a real BMW code reader I'm concerned at my limitations in diagnosis. So I'm going to take it in to the shop and ask them to scan it, and hopefully they will tell me if it's something I can work on myself.

I'm really quite worried that this could result in them suggesting 4 new coils, 6 new injectors, a fuel pump, a computer, 2 more new coils since I've now ruined the new replacements, 6 more spark plugs for the same reason, etc. etc. etc.

[PichaDis11]

Alrighty this isn't good much. There's probably much more going on but your scanner isn't telling/not capable of. What are you using to retrieve codes?

[Ranger Hoopy]

I have a simple OBD2 reader that was probably the cheapest one available when I bought it's ten years ago. I took the car in to my local and asked them to scan it- the mechanic felt confident before doing anything that this was related to the four old coils needing to be replaced, and scoffed at the idea of injectors being involved. His post was that cars without a Direct Injection rarely experience injector issues, so a 335 might have that issue but not my 330. I recognized that the two cylinders I was getting faults on, 2 and 4, probably had the old coils, and moved the two new ones to those for more troubleshooting. That didn't do anything, same faults on my reader, although I am troubled that I failed to clear those codes from the reader, so a better scan was certainly called for. He came up with misses on 1, 2, and 4, but also said that at least one of the coils hadn't been fully inserted! (I do have to admit I find the new style coils more challenging than the old ones with their satisfying 'click,' but I haven't yet observed one that wasn't pretty clearly "not in" or "as in as it could go."

So now I have replaced the four remaining coils, and hopefully that's the end of the story, but the garage was clearly having some inter-office communication failures, so I'm not 100% confident on the completeness of the diagnosis, and haven't yet put the airfilter bits back in to actually drive it.