[joekitch]

warning; slightly longer than average post, but trust me its a good mystery;

so i was getting some misfires on cylinder 5 starting in like mid February. started at first at WOT and eventually i'd get some whenever i stabbed the throttle too hard. every time i'd eventually get cylinder deactivation and the check engine light would come on, along with the engine shaking pretty badly at any rpm above 1.5k....pulling over and restarting the engine fixed it

scanning for codes, it was a misfire on cylinder 5, so i resigned myself to replace the spark plugs and the cyl 5 coil......eventually. It's at 90k miles so i figured its their time anyway.
it was cold as balls for the next few weeks, i dont have a garage, and i only got around to actually doing the job this past wednesday

pulled the old plugs and coils, didnt notice any obvious scarring or burning or carbon buildup or anything out of the ordinary really. the cyl 5 plug looked exactly the same as the rest....
but immediately after putting in the NGK sparkplugs and new coil for cyl 5 and starting the engine, i was getting EXTREMELY rough idle, what i can only assume was lots of misfiring. running codes again it was still on cyl 5?? so i swapped the new coil to cyl 1 and the cyl 1 coil to 5. problem went away. so i buttoned the engine up and called it a success

however over the past few days i'm still getting what i THINK are misfires, especially when stopped at stoplights or slow speed parking lot maneuvers. rpms dip for a split second and the car makes a tiny "shudder". these can happen in succession or spaced out over a few seconds. They happen more often when i'm turning hard left or right for parking maneuvers, or if i'm in drive with the brake depressed.
NO PROBLEMS at high rpms, i can tach it up and down no issue.
when i can for codes NO ENGINE CODES come back, looks clean

-so what the heck is going on?
-are my cats clogged from that month of occasional misfires?
-are the sensors responsible for picking up misfires just not working?
-and why did putting a new coil on #5 make things WORSE until i swapped with #1?

let me know if you need video of the misfires at idle or anything like that

[joekitch]

CRAP, more data;
just got a misfire+cylinder deactivation+check engine light while driving to work today, immediately pulled over and turned off the engine and ran a ghost code scan, cyl 5 misfire AGIAN.

so basically a brand new coil causes cyl 5 to misfire tons, and an older working coil causes it to misfire occasionally anyway

what the heck?!

[Aashenfox]

Try this...

http://www.e90post.com/forums/showthread.php?t=986168

also, I heard that stock cars on the cooler NGKs can have issues in winter due to the colder plug rating, but I'm no expert. In any case, the first thing I'd do for a misfire is replace with oem plugs. Having said that, since changing the coils around didn't change anything, my mind went to the thread I linked above...

[joekitch]

Originally Posted by Aashenfox

Try this...

http://www.e90post.com/forums/showthread.php?t=986168

also, I heard that stock cars on the cooler NGKs can have issues in winter due to the colder plug rating, but I'm no expert. In any case, the first thing I'd do for a misfire is replace with oem plugs. Having said that, since changing the coils around didn't change anything, my mind went to the thread I linked above...

hmm, certainly possible, but i have a 2008 auto 328xi, whereas that thread seems to be centered around 2007 manual coupes?

[Aashenfox]

Sorry, I have a terrible habit of assuming everyone has N54s, side effect of many years spent on specific model forums for other cars. I don't think the tranny has anything to do with it though, but again I may be wrong.

[joekitch]

Originally Posted by Aashenfox

Sorry, I have a terrible habit of assuming everyone has N54s, side effect of many years spent on specific model forums for other cars. I don't think the tranny has anything to do with it though, but again I may be wrong.

well, if i have the same ECU its certainly worth a look, however since i'm only getting a cylinder 5 misfire and nothing else, i dunno.

is there any resource anywhere saying what ECU i have based on year and model?

[joekitch]

another possibility i'm reading, fuel injector issues?
apparently it can be diagnosed by just swapping injectors, just like diagnosing coils, and thankfully they're as easy to replace as coils (pop the injector rail, pull a bolt, injector is out) so this may be an easy way to see what's up.

before i do that however, are there any other diagnostic means available to me? or simple tests that would indicate injector and not something else?

and of course all these fuel injector problems seem to be EXCLUSIVELY with the 335i (n54) so that casts some doubt

[Aashenfox]

realoem.com I guess for your DME version.

P.S. I'd say you answered your own question there, since its easy to swap injectors over, try that first, see if the problem follows the same injector.

[joekitch]

Originally Posted by Aashenfox

realoem.com I guess for your DME version.

P.S. I'd say you answered your own question there, since its easy to swap injectors over, try that first, see if the problem follows the same injector.

http://realoem.com/bmw/partgrp.do?mo...55&hg=12&fg=10
welp, looks like i have an msV80, not an msD80 like in the n54, so that removes another potential fix

and i'm still really confused about the very rough idle and misfires right after putting a BRAND NEW BOSCH COIL into cylinder 5, and it going away after swapping an OLD coil onto cylinder 5. This seems like it could be a key piece of info for diagnosis but what could it be?

[joekitch]

ok, called up a local expert (5 star rated nearby indie mechanic on bimmershops.com), and what he said was basically

*almost certainly a coil or spark plug issue still
*might be poorly gapped spark plugs, which is odd because NGKs are pre-gapped but occasionally they'll get bumped around during shipment and screw up the gap slightly
*probably just need to replace the other five coils instead of just the one on #5
*he recommended dropping it by his shop for about half an hour to run some intensive diagnostics on the cylinders in general, just monitoring them during idle and driving. from there he'd be able to say with assurance what the problem is, and if its anything more severe than just coils/plugs

[thomas88162]

Don't ever assume anything. Just because the N52 uses more reliable, ported injectors does not mean they cannot fail. If the plugs appear to be correctly gapped, injectors are the next place I would look. Also, make sure that your coils clip down fully on the spark plugs as a partial connection could cause this.

[joekitch]

Originally Posted by thomas88162

Don't ever assume anything. Just because the N52 uses more reliable, ported injectors does not mean they cannot fail. If the plugs appear to be correctly gapped, injectors are the next place I would look.

well, the indie shop fellow did state that out of possibly 600 n52 e9xs he's seen with symptoms like this, only ONE had a bad injector. so the probability of that is very tiny compared to other factors i haven't explored yet

[thomas88162]

Originally Posted by joekitch

well, the indie shop fellow did state that out of possibly 600 n52 e9xs he's seen with symptoms like this, only ONE had a bad injector. so the probability of that is very tiny compared to other factors i haven't explored yet

Use all of the probability you want, but you have no idea until you really look at things. Experienced eyes are everything to making repairs. Rule nothing out until you can prove otherwise. Try a cheap gap gauge on the plugs, whether they spec out or not proves them good/bad. If nothing else, try that indie as they have a higher probability of knowing what to look for.

[joekitch]

update; i bit the bullet and just ordered a full set of coils
backed out the NGK plugs and confirmed they were all gapped to 0.040, none of them lost gap
slapped in all new coils
no more misfires! and previously (before the misfires) it ran a little rough at idle, little bit of shaking, however that seems to be slowly going away. i've driven about 400 miles on the new plugs so far

[Rollo`]

I had this problem a couple of months ago...still CPO so dealer changed the problem coil. While I was there the mechanic said BMW recently issued a directive to replace all coils when you replace one but the dealership didn't have them to do it.

So a month later it happens again--again they didn't have the coils to replace all so they replaced one, problem cleared up for a few weeks and now it has happened again. but this time it is missing but hasn't totally failed and triggered the check engine light.

I plan to drop it at the dealer on Thursday and they are supposed to replace the remaining coils for me...thinking of having them replace the plugs while they are doing it. Hopefully that clears up the problem once and for all.