Misfire - Crank sensor?
Printed From: Bavarian-Board.co.uk - BMW Owners Discussion Forum
Category: Technical & Model Specific Forums
Forum Name: BMW 5 Series
Forum Discription: This forum will deal with any issues on the BMW 5 Series (E12, E28, E34, E39, E60 & E61)
URL: http://www.bavarian-board.co.uk/forum_posts.asp?TID=47250
Printed Date: 30-June-2024 at 20:05
Topic: Misfire - Crank sensor?
Posted By: 540 V8
Subject: Misfire - Crank sensor?
Date Posted: 03-October-2010 at 20:39
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Ok, I'm re-visiting this one. After having new tyres, lower front arms and a brake accumulator fitted, finally excorcising a few gremlins, I really need to face the misfire issue I still have after what must be over 2 years now. I am 90% sure it is not a cylinder that is down as the misfire doesn't seem confined to just one. If I disconnect each coil pack in turn, the engine runs rougher on all 8 cylinders hence my theory it's something to do with the ignition control or fuelling rather than a coil pack or injector. If the car is plugged in, there is a stored fault of crank sensor which has been replaced. The fault then stays away when cleared until the engine is revved to about 4000rpm then the engine management light flicks on and the power dies for a second until rev drop, that is when the fault for crank sensor shows back up. I have shone a torch on my front crank pulley while the engine is running (where the sensor reads the signal from) and I can see quite clearly it doesn't run 100% true so my theory is due to the uneven wobble of the pulley, once the revs reach so high the crank sensor can no longer read the teeth on the wheel and the engine cuts the power for a second until it manages to read the teeth again. I know replacing the pulley would more than likely cure the engine not revving high but could this also be the source of my engine misfire, even at idle? Can a worn front crank pulley cause the signal to have the odd 'blip' i.e. miss a tooth and cause a small misfire? I'm really hoping that I may finally put this one to bed, my worry is that if it doesn't it may end up costing me much more money to get it into a specialist  ------------- 
Current:E34 540i Touring 6 speed manual(Mpower bodykit & suspension)& Chrysler Voyager 3.3 V6 auto Previous:E34 530iSE AC Schnitzer suspension. E28 525e auto-Standard |
Replies:
Posted By: Andrew Rolland
Date Posted: 05-October-2010 at 17:15
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A wobble in the crank pulley doesn't sound an unjust cause. Proving that it is the bit at fault will be difficult. I'm guessing a new pulley will cost plenty and it will be torqued up to a horrendous amount of Nm/lbsft, making swapping it an expensive difficult task....but one which may indeed cure it. I thought you sorted your missfire when you found a loose/corroded engine electrical plug? Or was that someone else??? I'm wondering if the pulley has bent slightly on account of someone previously changing the belts and levering at the belt to get it on or off? ------------- Be exclusive and drive a Petrol 5 Series! Current '13 62 F10 535i MSport Auto Previous '04 04 E60 545i SE Auto '03 53 E60 545i SE Auto (Stolen) '98 S E39 523i SE Auto |
Posted By: 540 V8
Date Posted: 09-October-2010 at 23:41
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The pulley is has a rubber donut around the centre and once this wears it can then cause the outer toothed ring to resonate meaning it doesn't run true. My theory was that if this isn't always running as close to the crank sensor as it should then the ECU cannot get a proper signal causing possible misfire and the revving issue. I was sure it is the cause of my engine not finding it's way past 4000RPM but that problem, again seems to have cured itself (that's the issue I thought had been cured by sorting the plug out but it returned a short time later) The part from BMW is over £300 but I have seen a guy on ebay selling them for most models for about £100 so for that price it's worth a roll of the dice. Perhaps I'll bite the bullet and just do it, that would eliminate another possible cause anyway. Mike -------------
Current:E34 540i Touring 6 speed manual(Mpower bodykit & suspension)& Chrysler Voyager 3.3 V6 auto Previous:E34 530iSE AC Schnitzer suspension. E28 525e auto-Standard |
Posted By: Hasso
Date Posted: 11-October-2010 at 05:53
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I hope you buy your cranksensor from BMW and not from independed sparepartsshop. Senors ABS/Camshaft and crankshaft from independed deliverys seems to be a lottery to buy and have give BMW owners a big headache fore a couple off years now. ------------- BR Hasso BMW 540T 2001 6 speed. BMW 316G (biogas) -1998 http://www.autopower.se/galleriet/bilder.asp?bil=40895 http://www.autopower.se/galleriet/bmw.asp?bil=45700 http://www.autopower.se/galleriet/bmw.asp?bil=40865 http://www.autopower.se/galleriet/bmw.asp?bil=45749 |
Posted By: 540 V8
Date Posted: 13-October-2010 at 20:08
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Yes, was a genuine sensor fitted and it made no difference at all. Mike -------------
Current:E34 540i Touring 6 speed manual(Mpower bodykit & suspension)& Chrysler Voyager 3.3 V6 auto Previous:E34 530iSE AC Schnitzer suspension. E28 525e auto-Standard |
Posted By: AndyMac2
Date Posted: 14-October-2010 at 15:12
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Hi, I have just replaced 6 plugs on a 2001 520i 2.2 with 4 of 6 pots misfiring. seemed to cure the prob after a difficult time getting her started (suspect glazed bore from fuel wash-down). Following day she started on 5, key off, key on, started fine. Any suggestions appreciated, cheers, Andy |
Posted By: Andrew Rolland
Date Posted: 15-October-2010 at 18:45
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Welcome to the forum Andy What are your coils like? Could really be anything from any one of the sensors to a duff coil. A diagnostic check is probably your best bet. Andrew ------------- Be exclusive and drive a Petrol 5 Series! Current '13 62 F10 535i MSport Auto Previous '04 04 E60 545i SE Auto '03 53 E60 545i SE Auto (Stolen) '98 S E39 523i SE Auto |
Posted By: jetsetwilly2000
Date Posted: 19-October-2010 at 11:32
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I'd say change the pulley. If you can see a wobble then it's got to be prime suspect. The fact that it currently revs ok might just be down to the disintegrating vibration damper having adopted a resonant frequency that doesn't affect fast running - but maybe does affect idling. bulletproofbomb, are you about? I think you were the first to post about this... ------------- E90 M3 DCT, E46 330d Touring, VW T5 wannabecamper Previous: Disco 3 TDV6, 2x E34 540i6, E34 535iS |
Posted By: AndyMac2
Date Posted: 20-October-2010 at 06:00
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Hi Andrew, Thanks for the message and info, all coils ok and diagnostics done and clear, car is going well now, cheers, Andy |
Posted By: bulletproofbomb
Date Posted: 20-October-2010 at 18:19
How strange- I had a funny feeling to check this forum today (after forgetting about it what with one thing and another) and my name is mentioned!  As you JSW2000, perhaps it is a resonance at higher speeds, though I think the gap is meant to be about 1mm max, so I'd expect to see some signs of impact if it is wobbling enough to affect things. I'll refresh myself on this topic later, as have to dash just now, but I can't believe it is still misbehaving.... My e34 530i has just decided to stop starting after a period of iffy starting when hot, so I think I'll need to buy a new Crank Position Sensor, and hope I have a smoother ride.... ------------- e34 540iT 6-speed |
Posted By: proxy10
Date Posted: 27-October-2010 at 07:27
that's what we call "hunch", or suffice it to say you have a bond with this forum. ------------- |
bulletproofbomb wrote:Posted By: 540 V8
Date Posted: 29-October-2010 at 22:35
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Sounds like the way forward. A new pulley it is then~!
Mike -------------
Current:E34 540i Touring 6 speed manual(Mpower bodykit & suspension)& Chrysler Voyager 3.3 V6 auto Previous:E34 530iSE AC Schnitzer suspension. E28 525e auto-Standard |