Yes ok, it's taken me six months to investigate my misfire but when you got 8 cylinders, you don't often notice it until sitting in traffic when you can feel the uneven judder of the engine and it's at that point I think "damn, must take a look at that!"

I also had the issue of not being able to rev over 5000rpm and the crank sensor not solving the problem I had to look at the wiring. I had suspected wiring so I got one of the technicians at work to wiggle the plug as I revved. This caused the engine to rev up to 6k then other times only up to 4k so definatley a loose connection. I tried bending the pins a little and closing up the female pins so it was more of a snug fit but to no avail. I decided to then cut the plug off completely and about 6 inches of wire either side of that to try and eliminate the bad connection. Four shrink fit terminals, some cable conduit and a couple of cable ties later, an engine that red lines properly for the first time since I got the car.

My second issue, the misfire, was possibly going to be owed to the fact my rocker cover gaskets were leaking oil and covering the plugs causing a bad spark. Upon inspection after removing all 8 spark plugs, one of the coil pack boots was missing the sealing lip at the bottom and as the plugs had about 25,000 miles on them, I'm guessing worn electrodes and no sheilding caused the spark to find the easiest route, i.e. the rocker cover!

New set of plugs and the perished coil boot replaced set the missing cylinder to smoke into life! A few damn good revs and a blast up the road saw the V8 clear it's throat and roar once again. I treated her to 30 litres of V-power and a bottle of injector clean which put a huge smile on my face all the way to work!

Although I didn't really think much of the missing cylinder power wise, I can now feel the difference having it back and boy does it feel good!

Now all I have to do is sort the rocker gaskets and the suspension squeek.

All in good time

Mike

Hi 540 V8

GLAD TO HEAR YOU GOT IT SORTED ...

Can I ask, what was the loose connection? The plugs that you speak of...are these the ones that plug into the coil packs or are you speaking about something else?

Thanks so much

BB

Good news Mike.

What drew your attention to that particular connection?

I know what you mean, after spending most of the previous week towing a trailer behind my V8, slowly so it didn't bounce about on the bad roads, she was finally let of the leash on Friday on my day trip return from Glasgow to Rannoch Station in the middle of Perthshire.

There is no such thing as no overtaking on the A9.

I hope the missing plug sealing ring didn't end up in the cylinder!

Sounds like it didn't, which is good.

It is quite scary to think of a big 4 litre V8 revving all the way up to 6700 rpm.  That is a lot of metal moving about very quickly.  I'm not sure if mine will rev that high.

All the best

Andrew

Great to hear your firing on all 8 again.

Have lots of smiles with all those horses

To clarify, this connector is on the bulkhead (the panel along the back of the engine which seperates the driver from the engine) just below the seal which runs along the top. If you were standing on the drivers side it's just to the left of the heater valves. The plug is clipped into a black c shaped clip.

I had it on a fault code reader and it gave the fault of a bad signal from the crank position sensor. After having this replaced and the fault still being present, I spoke to an ex BMW technician who told me it was possibly (though unlikely) an ecu fault or a bad earth/connection between the ecu wiring and the sensor. I had a hunch the weakest place would be this plug which is more at risk from vibration than anything else. After trying to make a better contact between the plugs with no success I opted to cut that section out and replace it with new wiring and connecting it using 2 heat-shrink connectors which solved that problem.

The misfire unfortunately has returned. I thought it may have been one of the coil pack rubbers which had failed but after replacing that and the plugs the fault is back. My next suspect it a coil! Now it's time to disconnect each coil in turn to find the culprit then perhaps see if I can find a donor coil I can use to test my theory. If it's right then it's a new coil, if I'm wrong, I'm guessing it's a pain staking wiring check.

Mike

Hi mike,

Sorry to hear your problem is back again but my reading your original post it made me aware of a similar problem i might have..

First of all my car idles at 500 when warm and car is quite shaky as a result of this. I had the computer on it and it came up no faults. When when the guy asked me to hold revs at 2000 his computer wasnt registering the revs properly. So he said this could be my idle valve. This has a little shutter door than lets the air in. He said its either faulty or the door is sticking causing a bad idle. I cleaned it with carb cleaner but no avail. Now im thinking maybe the problem u have is whats wrong with mine.........

On satursday past I MOT'd my car. Upon him revving it a couple of the other mechanics came over and said my car is missing. 1 guy said it sounds like a cylinder is down. But I have noticed there is oil running down from the bolts at the top of the engine (Not the rocker gaskets, its the bolts above it). Its the rubber washers needs replacing. But im thinking the oil is running down into the plugs and fouling them casuing the missing and the bad idle!!

Im going to investigate it at the weekend, Im going to replace the rubbers, clean out around the plugs and coils and fit new NGK plugs. I'll let u know how i get on........

Good luck with yours and let me know how you get on

Cheers Mike

stheaney2007 wrote: Hi mike, Sorry to hear your problem is back again but my reading your original post it made me aware of a similar problem i might have.. First of all my car idles at 500 when warm and car is quite shaky as a result of this. I had the computer on it and it came up no faults. When when the guy asked me to hold revs at 2000 his computer wasnt registering the revs properly. So he said this could be my idle valve. This has a little shutter door than lets the air in. He said its either faulty or the door is sticking causing a bad idle. I cleaned it with carb cleaner but no avail. Now im thinking maybe the problem u have is whats wrong with mine......... On satursday past I MOT'd my car. Upon him revving it a couple of the other mechanics came over and said my car is missing. 1 guy said it sounds like a cylinder is down. But I have noticed there is oil running down from the bolts at the top of the engine (Not the rocker gaskets, its the bolts above it). Its the rubber washers needs replacing. But im thinking the oil is running down into the plugs and fouling them casuing the missing and the bad idle!! Im going to investigate it at the weekend, Im going to replace the rubbers, clean out around the plugs and coils and fit new NGK plugs. I'll let u know how i get on........ Good luck with yours and let me know how you get on Cheers Mike

Well I can tell you, a cylinder missing is hard to spot on a V8!

If I sit in my car with the doors shut and just let it idle, listening very carefully, I can just about hear a gap in what is otherwise a smooth hum and of course there is a slight judder through the car but not really noticable when the throttle is fully open!

I'll be interested to see how you get on. I'm suspecting either a coil or injector at this point. I'm going to disconnect each coil in turn to pin point which cylider is missing then I'll swap the coil with another one to try and determine if it is the coil or another fault. I'll keep you posted.

Mike

mike,

since i last spoke to you I've had a few problems. Up until yesterday mine was exactly like yours. A slight miss, MOT guy said its missing a cylinder. I never noticed it. So yesterday I took the covers off and found the the round rubber washers are leaking. One of the plugs is swimming in oil. So i thought YES, I can fix it and finally have all 8 cylinders for the 1st time. BUT

I ordereed 8 new NGK plugs, dried out all the oil,  got new washers from BMW and replaced all of them. Fitted the new plugs, now is missing more than 1...... This is so frustrating. So earlier I took each plug out 1 by 1 and held it against the block. All 8 are sparking solid. So this means all the coils and plugs are perfect. So how the hell is the missing really bad now? I noticed the leak is back slightly. One of the plugs was wet. I have a leaking gasket as well on the driver side bank of cylinders. But this should not matter in the short term. I dried the plug and lead off and its sparking perfect. i put it back in and is still very bad....worse than its ever been.

When I start up its idling worse now. When I goto put in drive the idle is now dropping to about 200 and the car dies. When I pull off its very bad and very missy. I can build up spead eventually where there is a bit of power but missing very badly.

When I jacked the car up after i done all the plugs yesterday i squashed one of the fuel lines from the back. I wonder am i restricting the fuel flow. But its not that bad the kink in the fuel line. i also tightened the screws on the petrol filters.

Its either this or when i took each plug out yesterday, I put a rag in and cleaned the spark plug housing, some fibres must have dropped in.

What about the fuel injectors them selves?

If you sparkers and coils are working, it could be a fuelling problem into one particular cylinder which would give the same symptom as being one cylinder down.

I had a fault on my Senator which had the dual ram intake system which is linked by a butterfly valve.  It was caused by the butterfly valve bouncing.  This meant that instead of the engine breathing as two 3 cylinder engines it was trying to breath as a 6 cylinder engines when it wasn't meant to be.

I know some 6 pot BMW engines have a similar system to what was in my Sennie but I have yet to hear about it on an 8 pot engine.

Could be some form of air leak elsewhere in the intake manifold but on the V8 that would be kinda complex to poke about it.

Best of luck sorting these faults guys.

Keep us posted

Andrew  

DSK328i wrote: excellent job .... many of us have misfires tahst are never properly cured but glad to see yours is back on proper form

Read further on chap!

Mike

stheaney2007 wrote: mike, since i last spoke to you I've had a few problems. Up until yesterday mine was exactly like yours. A slight miss, MOT guy said its missing a cylinder. I never noticed it. So yesterday I took the covers off and found the the round rubber washers are leaking. One of the plugs is swimming in oil. So i thought YES, I can fix it and finally have all 8 cylinders for the 1st time. BUT I ordereed 8 new NGK plugs, dried out all the oil,  got new washers from BMW and replaced all of them. Fitted the new plugs, now is missing more than 1...... This is so frustrating. So earlier I took each plug out 1 by 1 and held it against the block. All 8 are sparking solid. So this means all the coils and plugs are perfect. So how the hell is the missing really bad now? I noticed the leak is back slightly. One of the plugs was wet. I have a leaking gasket as well on the driver side bank of cylinders. But this should not matter in the short term. I dried the plug and lead off and its sparking perfect. i put it back in and is still very bad....worse than its ever been. When I start up its idling worse now. When I goto put in drive the idle is now dropping to about 200 and the car dies. When I pull off its very bad and very missy. I can build up spead eventually where there is a bit of power but missing very badly. When I jacked the car up after i done all the plugs yesterday i squashed one of the fuel lines from the back. I wonder am i restricting the fuel flow. But its not that bad the kink in the fuel line. i also tightened the screws on the petrol filters. Its either this or when i took each plug out yesterday, I put a rag in and cleaned the spark plug housing, some fibres must have dropped in.

Oh dear, sorry to hear that! I can only think that either your crushed fuel line is one possibility, you may have to eliminate that before looking elsewhere depending on how bad it is.

The other thing could be you have left the plug(s) to the coil(s) loose, disturbed a loose connection withing the wiring or perhaps one or more connecting rubbers between the coils and plugs are damaged?

They have a little spring loaded plate which contacts the plug. Perhaps one or more of the springs are too compressed and not making proper contact when in place. I have had to replace one of mine because it was perished but I have the other 7 anyway so will just replace them in the hope it will help.

My only other thought for my problem is an injector or worse case scenario (though VERY unlikely considering I had a new alusil block 70,000 miles ago) a compression problem.

My oil leak is only very small and only 2 plugs had a slight smear of oil on them so very unlikely that is my cause.

This weekend I am going to replace my other 7 coil connectors to the plugs and see if it cures it. If not I am going to unplug each coil in turn and see which one doesn't cause the engine to run even rougher i.e. pinpointing which cylinder is at fault then I'm going to move the coil from the suspect cylinder and see if the problem moves.

I'll keep you posted.

Mike

hi mike,

Ya you might have a point there about the coil connectors being pushed up too far and not making contact. That thougth did cross my mind as when i took the first coil off i didnt hear a popping sound from the plug (like the old ht leads in the older bmw's where the ht lead pushed onto the plug). But I know now that the 540i coils just rest on the plugs. I did try to force a plug to pop in. I wonder could I pull the connector in the coil downward to make better contact or would I end up breaking it. I have ordered 2 coils from ebay there 10 minutes ago which came off an e46 (coils are the same). I'll try them when I get them.

Anyway at the weekend i'll investigate. Im going to replace the metal fuel lines to rubber, change the 2 filters....then see what happens from there. My mate is a mobile electrician so i'll get his computer on it,

I'll let u know what happens

cheers

Well I got to admit, I'm rather confused right now. As I'd already bought them, I decided to replace the other 7 coil connectors (already did 1 a few weeks ago as it was mullered) just to see if the running was any different.

After changing all 8 in total now there is still no difference to the running of the engine.

So then I thought before I replaced the covers I thought I'd try and disconnect each coil in turn to assertain which cylinder is misfiring, my theory being when I disconnect the coil corresponding to the misfiring cylinder there would be no difference whereas when I disconnect the other 7 I should notice the engine running rather lumpy yes? ....er.......NO!  the engine ran noticeably lumpy with all 8 cylinders!

My conclusion?

MY CAR HAS NO FECKIN MISFIRE

I was always told a V8 should run so smoothly that there should be no shudder or vibration. I think it's all a case of suggestive thinking. Someone has told me I have a misfire when accelerating (which I always thought was a slight wheel balance problem) and from there is has spiralled into me picking the slightest little shudder to be a misfire (although I still do have the issue of it not passing the MOT for over 30 minutes extra due to the emissions failing)

I am really not sure but I don't think there is a misfire. The only other slight worry I do have is if it's been left for a few days, when I start her up there can be a bit of a cloud of smoke at first but that's literally as she fires into life and is fine all other times.

With all that said, any ideas on the above?

Stheaney, how did you come to the conclusion you had a misfire and wheat symptoms do you have i.e. does the car shake a lot, any noises, juddering, smoke etc?

Yours truly puzzled,

Mike

I agree with you...the smoothness of the V8 is over-rated I think...

Yes, they do have a smooth idle compared to the 6 and 4 cylinder cars, but it is by no means perfect...

Even when my car runs perfectly, and is firing on all 8, you can still feel an 'engine wobble' when she is idling...even Clarkson talks about the attraction to a V8 being that the idle is a little rough and not quite on 'time'...

Rawdon

I think there is still an underlying problem Mike.

You said it failed its MOT due to emissions and it chuffs out black smoke on start up.

You obviously feel the car just isn't quite right when you drive it. 

I would take a guess at a fuelling problem rather than an ignition problem. 

I would take some Wynnes Carb and fuel injector cleaner to the throttle body and any exhaust gas recirculation valves, crank case/cylinder head breather hoses. At your age of car things might be a bit blocked up.

Also give it a good few tank fills of Shell VPower that will help clean things out.

Andrew

I agree with the last poster there has to be another issue. My 540 idles asolutly smooth on startup and only when I stand in traffic for a long time (aircon of) does the car have a very very smal shake that disapears as soon as I drive it for a couple of hundred yards.

It's a bit of a pain but a compression check might always be a good idea just to rule things out. The crank breather system (called a cyclone valve) is known to act up on these and the symptoms are the same as for a low compression block. Injectors could be clogged up the pressure regulator might be on it.s way out the o2 sensor should be changed every 50k miles and you need a proper tester to see if they are ok lastly the AFM might be bad.

Most of this can be checked in a garage (or from you if you have the tools)

HTH

Chris 

Chris has said the things I was trying to say, glad someone knew what I meant.

Mine has a slight wobble as too did my previous E60 (that was stolen with the keys from a BMW dealer) when hot just as Chris has said.

It must be fuel related, black smoke, poor emissions.  I was thinking about this on the train back from Edinburger this morning.

Have you had it plugged into a diagnostic machine when the car has been driven.  This should give you read outs of all the sensors so you could tell what say the AFM is reading or the O2 sensor etc.  Obviously you you would need a helper to either drive or read the hand held diagnostic machine in the car.

Andrew

Andrew Rolland wrote: I think there is still an underlying problem Mike. You said it failed its MOT due to emissions and it chuffs out black smoke on start up. You obviously feel the car just isn't quite right when you drive it.  I would take a guess at a fuelling problem rather than an ignition problem.  I would take some Wynnes Carb and fuel injector cleaner to the throttle body and any exhaust gas recirculation valves, crank case/cylinder head breather hoses. At your age of car things might be a bit blocked up. Also give it a good few tank fills of Shell VPower that will help clean things out. Andrew

Already done the two things you suggested Andrew, I used injector cleaner when I changed the plugs a couple of weeks ago and I have been running her on V-power for the last year or so.

The smoke upon start up is like a grey/blue colour and smells like fuel, i.e. running rich but literally the secong she is running after firing up all seems ok. I'm trying to guage what is classed as rough running.

If I sit in the car with the engine running as with any car, there is some vibration from the engine, it's the nature of the beast, engines make noise and shake, fact! but I can't work out whether mine is running rough ir it's all in my head?!?!?!?

I wish I knew of another 540 owner who lives local so I could compare them but I think you guys are out of reach for me.

I think you are definatley right about the possible fuel problem though Andrew purely based on the smoke smelling of fuel on start up. I will perhaps start looking at cleaning my breather hoses and checking the vacuum pipes for leaks too.

I will solve this mystery dammitt!!!

Mike

Andrew Rolland wrote: Chris has said the things I was trying to say, glad someone knew what I meant. Mine has a slight wobble as too did my previous E60 (that was stolen with the keys from a BMW dealer) when hot just as Chris has said. It must be fuel related, black smoke, poor emissions.  I was thinking about this on the train back from Edinburger this morning. Have you had it plugged into a diagnostic machine when the car has been driven.  This should give you read outs of all the sensors so you could tell what say the AFM is reading or the O2 sensor etc.  Obviously you you would need a helper to either drive or read the hand held diagnostic machine in the car. Andrew

I have had it plugged in a couple of times and the only fault it showed was crank sensor which has now been sorted.

I'm going with your fuelling theory Andrew and as mentioned in my previous post, i'll start with breathers and hoses (filters were changed last service so I know it's not them) and see how I go.

Mike

Hi Mike

the cyclone valve (crank breather) will not trow a fault code if it's on it's way out. However the car will start using oil if it gets worth. The o2'sensors and or cat's will only trow up a fault if they are realy bad but you should be able to check them in a garage that has a gas analyzer and a fast reader for the o2 sensor values as they cxan see how fast the values change when you rev the car.

Hope you find the problem soon

Chris

Nice one Chris, I'll check that out. Where would I find this breather and where does the breather pipe go from/to?

Cheers

Mike

the valve is screwed into the back of your intake manifold

its no 3 in this picture

http://www.realoem.com/bmw/showparts.do?model=HK32&mospid=47398&btnr=11_1498&hg=11&fg=40 - http://www.realoem.com/bmw/showparts.do?model=HK32&mospi d=47398&btnr=11_1498&hg=11&fg=40

you probably need 4 and 5 as well when you take it apart.

HTH

Chris

Hmm how much stripping would you need to get at that bit? 

Would you need to take the whole manifold off as on mine you are right at the bulkhead and access would be a tad tricky.

I really must have a poke about my engine, still haven't got the top cover and spark plug covers off yet.

Andrew