Intermittent misfire

Coupes66

Corporal
Dec 26, 2017
147
108
50
Ride
BMW 335i N54
Over the past 5 weeks, I have been trying to solve an intermittent misfire/backfire on my car. It can be running ok and at the blink of an eye, it will have misfires on all cylinders. I sometimes start it in the morning, and it will instantly misfire and backfire. Get the revs up to 2,000-,2500rpm for a while and it will stop misfiring and idle normally. Other times, I will turn it off while it is misfiring/ backfiring, start it in the morning and it will run perfect for a day before playing up again. In attempting to solve the issue, I have replaced the O2 sensors, spark plugs, Index 12 injectors with my old index 10 injectors, CP and intake manifold sensors, hpfp with my old one which was still working ok, EKPM2 for a EKPM3, vanos solenoids and cam sensors and hp fuel rail sensor. I will get a new crankshaft sensor next. I am thinking it could be a timing issue such as a faulty vanos. The other day while cruising at 100kph, the engine light came on, with a DTC 2A87 which is the exhaust vanos mechanism. I stopped the car, turned the engine off, cleared the code and it ran without an issue for the remainder of the trip. The following datalogs are from driving it home while misfiring and idling while misfiring.

datazap.me | Coupes44 | Datalog.160223.3

datazap.me | Coupes44 | Datalog.160223

Any ideas will be greatly appreciated.
 

Jeffman

Major
Jan 7, 2017
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I would also try cleaning the vanos oil filter on the right side of the engine. It also could be carbon buildup on your intake - when was the last time it was Walnut blasted?
 

Coupes66

Corporal
Dec 26, 2017
147
108
50
Ride
BMW 335i N54
I would also try cleaning the vanos oil filter on the right side of the engine. It also could be carbon buildup on your intake - when was the last time it was Walnut blasted?
Thanks Jeffman. I intend to check the vanos filters next. The engine has only done 3,000kms since the intake ports were cleaned so that isn't an issue. If the vanos filters are ok, my next move is to change the exhaust camshaft vanos unit.
 

Brule

Sergeant
Feb 20, 2017
371
440
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335i 2007 6spd manual
The intake and exhaust vanos are both tracking perfect in them logs.

I couldnt see any problematic items in the data.

If you can add timing for each cylinder might help.

Its a weird one.
 

Coupes66

Corporal
Dec 26, 2017
147
108
50
Ride
BMW 335i N54
The intake and exhaust vanos are both tracking perfect in them logs.

I couldnt see any problematic items in the data.

If you can add timing for each cylinder might help.

Its a weird one.
Hi Brule. This issue certainly has me stumped the way the engine can be running perfect one second and the next, it is misfiring on all cylinders and backfiring. Then it can go back to running ok again. I can only think it is some timing issue for that to occur. I have checked the vanos filters and they don't look clogged but I gave them a clean anyhow. I am going to change the exhaust cam vanos unit next only because the 2A87 DTC came up. If that doesn't fix it, I am lost at what else to look at.
 

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Brule

Sergeant
Feb 20, 2017
371
440
0
Ride
335i 2007 6spd manual
Ignition coil wires, earth loose.

In them logs you had no cylinder timing corrections logged so couldnt tell when it mis fired besides drop in rpm while throttle was stable.
 

Brule

Sergeant
Feb 20, 2017
371
440
0
Ride
335i 2007 6spd manual
Is it the same cylinders mis firing?
All random cylinders?
 

Coupes66

Corporal
Dec 26, 2017
147
108
50
Ride
BMW 335i N54
Ignition coil wires, earth loose.

In them logs you had no cylinder timing corrections logged so couldnt tell when it mis fired besides drop in rpm while throttle was stable.
Ignition coils appear to be ok. I replaced the cylinder timing corrections with the vanos readings and the LTFTs but there were no timing corrections on any cylinders.
 

Coupes66

Corporal
Dec 26, 2017
147
108
50
Ride
BMW 335i N54
Battery voltage?
Battery has never been a problem while this issue has been present. Engine has always started straight away even when it is misfiring. I just checked the battery voltage after sitting for a couple of days and it is 12.2V.
 

Coupes66

Corporal
Dec 26, 2017
147
108
50
Ride
BMW 335i N54
Dear friend, faced this problem for more then 1 year. I solved my problem installing the OEM spark plug for this engine. Before that I drop away a lot of money buying others unecessary parts.

I have used NGK ILZKBR7B8G spark plugs gapped at 0.018 " for the past couple of years without any issues so I cannot see it being a spark plug problem especially when the engine can run fine for a day and then in a split-second start misfiring on all cylinders and after a period, for some reason it will come good again.
 

Brule

Sergeant
Feb 20, 2017
371
440
0
Ride
335i 2007 6spd manual
Its a weird one.
How do timing corrections look when its miss firing?

All drop 5 degrees at the same time or are they randomly pulling 2 or 3 degrees?
 

Coupes66

Corporal
Dec 26, 2017
147
108
50
Ride
BMW 335i N54
Its a weird one.
How do timing corrections look when its miss firing?

All drop 5 degrees at the same time or are they randomly pulling 2 or 3 degrees?
There are no timing corrections. The attached datalog has the timing corrections for cylinders 1-4.
What is your thoughts on the rail pressure? Does your rail pressure oscillate up and down like mine?
 

Coupes66

Corporal
Dec 26, 2017
147
108
50
Ride
BMW 335i N54
During this week, I reinstalled the newest HPFP as my old HPFP didn't make any difference. I replaced the rail pressure sensor, crankshaft sensor and exhaust camshaft vanos unit. When I last turned the engine off early in the week, it was misfiring but when I started it up, it idled and ran without any misfires. I took it for a 35km run where the speed varied between 40 and 80kph with a few stops and starts at lights without any issues. Datalog below

datazap.me | Coupes44 | Datalog.260223.1

After lunch, I decided to go down to the local Supercheap store and when I started the engine, it began to misfire. I raised the revs up to 2-2,500rpm for a couple of seconds and the misfire stopped and I completed the trip there and back without any issues. I did a log on idle when I returned.

datazap.me | Coupes44 | Datalog.260223.3

So my intermittent misfiring issue appears to still be there. I have run out of ideas on what can be causing this. Any suggestions?
 

Coupes66

Corporal
Dec 26, 2017
147
108
50
Ride
BMW 335i N54
I started the engine this morning and it had an intermittent misfire which went away after raising the revs to 2,000rpm for a couple of seconds. I let it idle and the misfire came back in and got worse. I logged the whole episode and found the actual degrees on the exhaust camshaft didn't follow the required degrees when the misfire occurred. The intake camshaft degrees is a straight line with no deviation between the required degrees and actual. If anyone has a log of the vanos units at idle on their engine, it would be great to see.

 

Coupes66

Corporal
Dec 26, 2017
147
108
50
Ride
BMW 335i N54
I am still chasing the misfire/backfire issue. The car ran fine for 5 days but then on day 5 in the final km driving home, a slight intermittent miss began. On arriving home, I let the engine idle and it was fine so I turned it off. The next morning as soon as I started the engine, there were misfires on all cylinders and backfiring until engine stalled. This continued every time I started the engine. On the next day, I logged the engine start up. Initially, it idled ok but as the revs dropped, it began misfiring and I had to pump the accelerator to try and keep the engine running but was unsuccessful. I started it again but it just cut out. The datalog shows the AFRs initially leaning out and the STFTs going up to 32 to counter this. The AFRs then go rich and start going up and down. I am at a loss on what can intermittently cause this. Any ideas?