[sim303]

Hi there

Thought appreciated on troubleshooting a bad misfire..

Last week, around driving back from holiday (~250mi) my 56 335i (49k miles) gave the odd hiccup during acceleration. Then after a few more miles, on the motorway, more hesitation and the CEL, and then limp mode and virtually no power, with severe engine vibration during the slightest acceleration and pretty much unable to go beyond 50-60mph. Essentially it felt like it had lost a cylinder, or more.

So I read the codes using BMWhat and got this:

Fehler: Misfire detection cylinder 3 in 2 Firing order / Failure detection cyl.5 / Misfire detection cylinder 3 in 2.Zuendreihenfolge
Code: 29CF


Thing is, I had "cyl 3 misfire" last year - to cut a long story short I replaced all plugs and the #3 coil. The warning code disappeared but hesitant performance continued (nowhere near as bad as now though), but that was fixed 100% when I had the engine walnut blasted. All was good. That was almost a year ago, but I've hardly used the car since - maybe 2000mi tops.

So before I read the codes this time I was ready to just replace the other 5 coils but that is strictly illogical since the fault is still on #3 (apparently).

How accurate are the error codes as far as pinning down a particular cylinder is concerned?

Another thought was injectors, especially as they could be fouled by the oil contamination (walnutting can't reach them). So one option is to send them off for ultrasonic cleaning. Any thoughts on that?

Beyond that I'm not sure. Any thoughts on course of action greatly appreciated. I'm happy doing my own work where practical (and generally prefer to do so so I can be sure what's being done).

Cheers all!

sim

[Phil325i]

The injector would get my vote. Have you had your car checked for a possible recall on injectors..?

[karlp]

Hi mate, had the exact same issues as you would always happen on a cold morning!
Turned out to be the solenoid, replaced and has been running fine ever since.

[windymissile]

Swap all the possible parts to see if the fault transfers to another cylinder.
-Take out coil 3 and put in in cyl 6. See if the fault transfers.
-If not, take out plug 3 and put it in cyl 6. See if the fault transfers.
-If not take out injector 3 and put it in cyl 6. See if the fault transfers.

These simple steps will eliminate the 3 main causes of misfires.

WM

[Briancanadiano]

Replace all your coils. I had a similar incident. Now problem free

[Josh1a1h]

I had this issue

I did it all in the end for peace of mind

New Spark Plugs,
Coil pack and all coils.

If its not that, then likely injectors...

GD LUCK and keep the thread update with your fix please

[old grey steve]

Like the others have stated coils are a reasonably firm favourite as are spark plugs, something more obscure as I had on mine is a cracked rocker cover(not to be mistaken with a rocker cover gasket but the actual rocker cover)as pictured below



Oil seeps down in to either the plug wells or can even contaminate an injector doesn't sound logical but where I work I've seen it on mine as well as a couple of other cars, as you can see once the covered removed you can see from the picture below what's exposed to a failing cover/gasket.




Worth getting a handle on the situation as you say it's cylinder 3 as has been said above worth at first port of call swapping coils(mark coil numbers before swapping as windymissile's suggested)so that a analysis can be done post doing this if it's coils happy days if this proves inconclusive it's worth looking at the plugs to check there condition and also to inspect the wells for oil while you're there plus looking around where the injectors are too again just to see if there's oil traces as the oil will as I've seen drip down the injectors, if you look at the last picture you'll see old oil on the actual rocker cover plus if you look at the injector you might be able to make out the shiny residue around the injector(which is oil)

[sim303]

Originally Posted by Phil325i

The injector would get my vote. Have you had your car checked for a possible recall on injectors..?

Yes I'm tempted to get the injectors ultrasonically cleaned anyway as it's not too expensive and judging by the amount of cack that was in the intake before I had it walnut blasted it would be piece of mind.

My 06 car predates the injector recall (2007 build dates) and nothing has flagged up on the outstanding recalls as of the last service, so I guess that doesn't apply to me.

sim

[sim303]

Originally Posted by karlp

Hi mate, had the exact same issues as you would always happen on a cold morning!
Turned out to be the solenoid, replaced and has been running fine ever since.

Is that the Vanos solenoid? I thoroughly cleaned mine when I first had problems around a year ago. None of the fault codes indicated vanos plausibility, although I know you have to take the codes with a pinch of salt! In my case though the problem seems to occur during a good long run, rather than from cold.

What led you to the solenoid? Fault code, or process of ellimination?

sim

[sim303]

Originally Posted by Josh1a1h

I had this issue

I did it all in the end for peace of mind

New Spark Plugs,
Coil pack and all coils.

If its not that, then likely injectors...

GD LUCK and keep the thread update with your fix please

Yep tempted to just bite that bullet! Will keep updated of course, although I can only really do stuff at weekends...

sim

[sim303]

Originally Posted by old grey steve

Like the others have stated coils are a reasonably firm favourite as are spark plugs, something more obscure as I had on mine is a cracked rocker cover(not to be mistaken with a rocker cover gasket but the actual rocker cover)as pictured below

Oil seeps down in to either the plug wells or can even contaminate an injector doesn't sound logical but where I work I've seen it on mine as well as a couple of other cars, as you can see once the covered removed you can see from the picture below what's exposed to a failing cover/gasket.


Worth getting a handle on the situation as you say it's cylinder 3 as has been said above worth at first port of call swapping coils(mark coil numbers before swapping as windymissile's suggested)so that a analysis can be done post doing this if it's coils happy days if this proves inconclusive it's worth looking at the plugs to check there condition and also to inspect the wells for oil while you're there plus looking around where the injectors are too again just to see if there's oil traces as the oil will as I've seen drip down the injectors, if you look at the last picture you'll see old oil on the actual rocker cover plus if you look at the injector you might be able to make out the shiny residue around the injector(which is oil)

Hah! I had exactly this fault last year! Cracked rocker cover exactly the same place as your pics show. Which now you mention it is I think in the region of cyl 3. Oil had pooled into the well and I did the best I could to clean it up, but maybe there's some residual fallout. When I had problems last year I did wonder whether the crack itself was causing poor performance due to loss of vacuum around the crank case etc.

Crumbs I hope it hasn't cracked again! - haven't looked yet!

Hopefully I can get a good look at the weekend.

sim

[Josh1a1h]

GD LUCK!

[old grey steve]

Originally Posted by sim303

Hah! I had exactly this fault last year! Cracked rocker cover exactly the same place as your pics show. Which now you mention it is I think in the region of cyl 3. Oil had pooled into the well and I did the best I could to clean it up, but maybe there's some residual fallout. When I had problems last year I did wonder whether the crack itself was causing poor performance due to loss of vacuum around the crank case etc.

Crumbs I hope it hasn't cracked again! - haven't looked yet!

Hopefully I can get a good look at the weekend.

sim

Yep cylinder 3. Tried a fix with the good old fashioned glue gun lasted 6 or so weeks

The cracks quite pronounced I spun my old rocker cover over before I launced it and you can see the way the units moulded perhaps there's an issue there for othes o discover later My new one looked no different though its a different part number. But bloody frustrating though and a ball ache in terms of what damage it can do to both potentually to the car and other components and your wallet if you've got no warranty

[sim303]

Originally Posted by old grey steve

Yep cylinder 3. Tried a fix with the good old fashioned glue gun lasted 6 or so weeks

The cracks quite pronounced I spun my old rocker cover over before I launced it and you can see the way the units moulded perhaps there's an issue there for othes o discover later My new one looked no different though its a different part number. But bloody frustrating though and a ball ache in terms of what damage it can do to both potentually to the car and other components and your wallet if you've got no warranty

Hi there, sorry I didn't get a notification so only just saw this.

Yeah I agree the rocker cover thing does seem to be a design weakness as mine went in exactly the same place.

Anyway I have news on my misfire....!

I took the car to the dealer for diagnostics and they have confirmed, apparently quite positively, that the injectors are toast. This does stack up as a) it would account for why the problem didn't clear after replacing the coil on the identified cylinder, b) my car had serious coke build up, (for which I had it walnut blasted), the implication being that there could well have been build-up or fouling on the injectors.

Anyway... the bad news: Injectors are not covered under the Named Component insured warranty! Cost - just over £1500. Independent garage was actually more! (each injector is £180 alone).

The better news: I told my dealer I'd have to put it on hold as I'm not using the car and most of the time it seems OK. Unprompted, they came back a day later and said they'd taken it up with BMW UK who approved a goodwill offer of £750 all in. Given that the parts alone are over £1k that I'm jumping at that chance!

The even better news: I asked them to investigate what I described as "symptoms of N54 wastegate rattle". I expected, at best, to have to argue the toss and get into a debate about "normal noises" etc., but to their credit they came back and said, "yeah, wastegate actuators are knackered, we'll book them in under your warranty". That is a massive win for me because that off-throttle rattling noise was really starting to grate and generally sounded sh!t, and the work required is BIG. (est. 12+ hrs).

So all in all I'm pretty happy, both with the situation and my dealer

sim

[old grey steve]

Originally Posted by sim303

Hi there, sorry I didn't get a notification so only just saw this.

Yeah I agree the rocker cover thing does seem to be a design weakness as mine went in exactly the same place.

Anyway I have news on my misfire....!

I took the car to the dealer for diagnostics and they have confirmed, apparently quite positively, that the injectors are toast. This does stack up as a) it would account for why the problem didn't clear after replacing the coil on the identified cylinder, b) my car had serious coke build up, (for which I had it walnut blasted), the implication being that there could well have been build-up or fouling on the injectors.

Anyway... the bad news: Injectors are not covered under the Named Component insured warranty! Cost - just over £1500. Independent garage was actually more! (each injector is £180 alone).

The better news: I told my dealer I'd have to put it on hold as I'm not using the car and most of the time it seems OK. Unprompted, they came back a day later and said they'd taken it up with BMW UK who approved a goodwill offer of £750 all in. Given that the parts alone are over £1k that I'm jumping at that chance!

The even better news: I asked them to investigate what I described as "symptoms of N54 wastegate rattle". I expected, at best, to have to argue the toss and get into a debate about "normal noises" etc., but to their credit they came back and said, "yeah, wastegate actuators are knackered, we'll book them in under your warranty". That is a massive win for me because that off-throttle rattling noise was really starting to grate and generally sounded sh!t, and the work required is BIG. (est. 12+ hrs).

So all in all I'm pretty happy, both with the situation and my dealer

sim

Absolute result that

[myboris]

Originally Posted by old grey steve

Absolute result that

Lucky you, I had the same problem, no goodwill gesture for me

[Juz5i]

Nice one mate. I would jump all over that deal too I reckon.

Where did you get the walnut blasting done? At the dealers?

[sim303]

Originally Posted by Juz5i

Nice one mate. I would jump all over that deal too I reckon.

Where did you get the walnut blasting done? At the dealers?

Sorry I didn't see your message! In case it's still of interest I didn't get the walnutting done at the dealer (they didn't offer it at the time). I went to TWG Automotive - I can't recommend them enough. Ask for Will.

sim

[germanwhip]

how much for the walnut blasting?

[Phil325i]

Originally Posted by sim303

I took the car to the dealer for diagnostics and they have confirmed, apparently quite positively, that the injectors are toast. This does stack up as a) it would account for why the problem didn't clear after replacing the coil on the identified cylinder, b) my car had serious coke build up, (for which I had it walnut blasted), the implication being that there could well have been build-up or fouling on the injectors.

Pleased you seem to be edging towards a solution. Just one comment on your theory that your excessive coke build-up may have been caused by faulty injectors. As your engine is DI, the injectors operate downstream of the backs of the valves, so any fouling of the valves/stems cannot be due to injector problems, but the operation of the crankcase breather system.

Ever considered an oil catch tank..?

[sim303]

Originally Posted by germanwhip

how much for the walnut blasting?

I don't remember the exact price, it was over a year ago, but around the £300 mark I think.


sim

[sim303]

Originally Posted by Phil325i

Pleased you seem to be edging towards a solution. Just one comment on your theory that your excessive coke build-up may have been caused by faulty injectors. As your engine is DI, the injectors operate downstream of the backs of the valves, so any fouling of the valves/stems cannot be due to injector problems, but the operation of the crankcase breather system.

Ever considered an oil catch tank..?

My phrasing was a bit poor, my theory was the other way round, that the fouling caused by breather issues not only reached the valves, but the injectors too.

I did look into an oil catch breather but didn't do it in the end. I did tripartite the breather valve in the rocker cover with a (hopefully) better engineered metal model I bought from the states.

However now that I realise the potential remedy is not just walnutting but possibly injectors too, I might be more inclined to look at the oil catch can too!

sim