E46 330ci Sudden major misfire at all revs and clunking noise

[Hellmet]

Before half an hour ago my car has been driving fine, no idle issues, no power issues, no misfires and no codes. Then suddenly while driving everything went lumpy, it has major misfires throughout the whole rev range and the engine light came on (This is not just running rough, it is practically undriveable). Idle is steady, no bouncing or stalling but I can hear a very obvious clacking sound when outside the car coming from rear of the engine/transmission area while in neutral. With the clutch pedal pressed in, the clanking goes away (Still misfires though).

Ive plugged it in and the codes thrown are misfires on cylinders 1,2, 4 and 5.

The engine is still very hot so I will have to wait until tomorrow to check anything, but I'm a bit unsure on what to check. it 'appears' to be getting fuel as it starts right up and I doubt air flow/vacuum is a problem as idle is steady and I have no o2 sensor codes. The metallic clanking definitely bothers me though, and the car is currently undriveable.

EDIT: I would like to add that this is not a general maintenance issue. In the last year and a half I have replaced plugs, valve cover gasket, vanos seals, oil, water pump, coolant, idler pulley, air filter, ETC ETC.

Any advice on where to start would be appreciated,
Thanks,
Penis,
Hellmet.

[nonturbodan]

The clanking sounds like transmission noise. If the engine is pissed off and running rough the trans can make strange sounds. I wouldn't worry about that.

Pull the DISA valve out of the intake manifold and have a look at it. That could cause these issues.

Penis,
Dan

[All2kool]

These cars are so damn temperamental. I've found they don't like to sit undriven for very long. I went to run an errand yesterday and started the car after it sat for a few days. Started up but was running like hell. SES came on in less than a minute. Read the code, P1347, 'Misfire #3 With Fuel Cutoff'. Cleared the code, restarted, everything fine. Ran my errand without incident.

I'm guessing an injector was stuck closed for a moment.

[Hellmet]

Ok, I've had a chance to check over the car now it's cold. I still have no idea what's wrong.

• I've checked the disa as nonturbodan said and it seems fine. The flap opens and closes as it should and it holds vacuum.
• The problem is multiple misfires across all cylinders, many of which get fuel cut-off. Most of the time it runs on just 3 cylinders, but they aren't always the same 3. Codes are 'misfire cylinder (*) With fuel cut-off.
• I don't have nor have I ever had any o2 sensor or lean codes on this car, this appears to be ignition related.
• Spark plug ground wire seems to be making good contact as well as battery ground. All electrics are OK. Spark plug wells are clean and free of any oil.
• For shits and giggles I tried unplugging the MAF, the car responded as it would with a healthy MAF.
• I did a compression test. Compression seems low BUT this could well be due to a cheap compression tester. All cylinders at 150psi apart from Cyl2 at 140psi and Cyl3 at 170psi. (Cylinder 3 was the first one I tested, could it be higher because of this?)
• Fuel is reaching the engine, as I can smell it until cylinders get cut off. It starts up instantly with no hesitation.
• Idle is steady (Very rough, but steady) and there are no symptoms of a major vacuum leak.
• Misfires happen across the WHOLE rev range.

What can I try next to diagnose this???

Thanks,
Penis,
Hellmet

[MarcoZandrini]

Test the fuel pressure at the fuel rail. It has to be at least 50psi at all engine speeds.

[Hellmet]

Tested the fuel pressure and it is at 48psi. I have read that 50psi +- 3 is ok

[Hellmet]

The car is still only running on 3 cylinders, and no new codes have appeared. Just misfire all cylinders and some with fuel cut off. Different cylinders get cut off each time but it's usually 3.

I have ordered a fuel pump as PM, but the pressure seemed within spec.

Is there anything else I can check? Could cam/crank sensor make all cylinders misfire without throwing a code?

[Hellmet]

I just hooked the car up to INPA and checked codes and all live engine values, including O2, vanos etc etc. Absolutely every single value from all the sensors are spot on and within accepted range. Not a single value is off apart from the 'Roughness' test which shows cylinder 1 to be abysmally rough, and 3 and 5 to be bad. 2, 4 and 6 were within accepted limits, but by the codes thrown, I imagine the bad cylinders will change. Codes are still only 'multiple misfires on all cylinders, some with fuel cut off'.

[nonturbodan]

I see no mention of ignition coils yet. These are a fairly common failure.

The smooth running values can be misleading. One dead cylinder will make the rest read rough as well. What you might try is moving the coils to different cylinders, clearing codes and checking to see if your rough cylinder follows that #1 coil.

Your compression test verifies that your engine integrity is good. Its either a fuel or ignition problem. I suspect a coil.

[Hellmet]

Hmmm, I have already replaced 3 coils as they soft failed, missing occasionally under load. As I previously mentioned, the 'roughest' cylinder in INPA was cylinder 1, and after moving the coils around the 'roughest' cylinder does seem to follow. I have gone ahead and ordered a couple of Bosch coils as it would seem that it's at least part of the problem. This is a tricky one to pick up as codes are for misfires on all cylinders and the only way of spotting any correlation is via the roughness chart on INPA.

It still seems unusual that 1 failed coil would cause the rest to misfire though. Anyway, I'll wait until they arrive and see what happens.

[nonturbodan]

The smooth running values for other cylinders are frequently affected by one dead cylinder. They're all running on the same crankshaft. You will never see a situation where you have a dead cylinder with fuel cut off and five other cylinders reading <1 on the smooth running values.

[Hellmet]

I can understand that, the thing that threw me was the fact that I'm getting misfires and fuel cut off codes on all the other cylinders too, not just the really rough one. Even so, the coil seems to be at least part of the issue. When it arrives and I can replace it I'll report back. Hopefully it's just that.

[Hellmet]

Ok I have fixed the issue and wanted to post it here for anyone else in the future. It turns out that multiple misfires on all cylinders, multiple misfires with fuel cut-off (all cylinders) and multiple misfires on startup (all cylinders) was caused by 1 faulty coil.

This has been a nightmare to diagnose, and was impossible to diagnose with any generic obd scanner or even aftermarket BMW specific scanners eg. (Carly, PaSoft) as all cylinders were misfiring. The ECU would completely shut down 3 cylinders at a time after they misfired enough times. The only way I was able to follow any kind of fault when switching coil packs to different cylinders was through the live 'roughness' graph that is available on INPA. EVERY other monitored parameter was correctly within spec.

The clunking seemed transmission related and has gone away completely now that the engine runs smooth again.

I hope this helps someone in the future, and maybe persuade someone to bite the bullet and set up INPA on their computer if they don't already have it.


Penis.
Rob.

[nonturbodan]

I usually recommend replacing them all at once. I have tried to do individual coils in the past and the remaining coils seem to fail one after another not much later. Last set I got for very cheap from AM Autoparts, surely straight out of China, has been working very well in the in laws' 528i.

[Sio2crew]

This describes my issues to the T.

Big shout out to the o.p.

Going to grab a new r8 coil pack or two tomorrow.

[xray1]

@hellmet
Was surprised to read one bad coil causing misfires on multiple cylinders but replacing them solved my problem!
Prior to replacing coils I replaced fuel filter and fuel pump on my e46. Fuel pressure was low anyways (42psi) so needed but not cause.
Big shout out to Hellmet for posting resolution!