Dropping a cylinder on tickover?

G

GreyZed

Senior member
 City of Makemland
Just recently I've noticed that when idling the Zed occasionally seems to miss a beat and I feel a bit of a clunk back through the car as if coming from the rear of the car(exhaust backbox wobble?).

I have replaced the plugs within the last 2 years with NGK Iridiums, so my initial thought was to replace all of the coil packs now as the car is 11 years old (even though only on 55k miles) but then I checked the price of them! So I thought let's just start with the cheapies so I looked into replacing the fuel filter - but this seems to be a 'for life' component based on where they've put it!

No warning lights triggered and I've not noticed any obvious performance issues on the move and this makes me think that maybe coil packs can't be the cause as surely it would do it while moving too and I'd notice?

Might still do the coil packs anyway but thought I'd have a punt in the dark with you guys to see if anyone has had and solved the exact same issue?

Thanks.
 
Could be the plugs again, plug technology isn't that much more advanced than decades ago and during this switch to longer maintenance intervals I don't think anyone told the plugs about it. If you're doing short/slow journeys it could be gunking up, have you tried to see if the problem is reduced by an Italian tune up? I recommend the A35 between Wareham and Poole for this.

If not, try pulling a plug or two from the end and middle and see what the colour tells you.
 
It will either be a coil or injector.

Iridiums last a long time and especially with you doing low miles I doubt its them at fault.

If the EML isn't being twigged by the fault then I would wait until it does, it will at least give you a direction to follow for diagnosis..
 
Thanks,

Having done a bit of research I've discovered that BMW had issues with Bremi coils (identifiable by being all black housings) but I have the silver/grey Bosch ones. Also it seems most people's experience of failed coils is that it seriously affects performance whereas my Zed is driving fine and just blipping down a cylinder now and again on tickover.

Maybe you're right with the injector suggestion. Maybe a good fuel system clean and a rolling road tune.

Miles wise I do 4 to 5k a year in the Zed. I always avoid doing any really short journeys where it would not reach normal operating temp but I regularly go to work in it which is around 12 miles each way.

What about MAF and lambda sensors. Could they cause the symptoms I am seeing.

Thanks again for the help guys.
 
Just in case anyone else has a similar issue I thought I'd report back on this issue. As stated above dropping a cylinder intermittently on tickover. Not missing on the move or at least if it was it wasn't noticeable and no error lights thrown. Eventually took the plunge and ordered 6 new coil packs as I came across an offer on Ebay for Bosch ones that worked out at £20 each delivered.

Issue resolved! :thumbsup:

My old coils were all Bosch but 2 of them had been replaced previously and were newer than the others. Car has only 55.5k miles on so I would suggest that coils degrade with age rather than use (unless you are doing mega miles). I don't understand why a dodgy coil would cause it to misfire on tickover but not on the move but it did.

Anyway happy to have a fully healthy Zed again and hopefully if anyone else is puzzled by the same symptoms this thread may now help.

Bosch part number 0 221 504 464 Ebay and some other websites showed E85 3.0i compatibility for this part number (coils are all black rubberised coating now).

RealOEM showed part number 0 221 504 470 and there are other variants quoted for the M54 engine on the internet and contradicting advice on some forums but I suspect they change numbers regularly as minor product upgrades are incorporated and they only differ mainly around the flexible ant eaters nose that sleeves the plugs. Anyway I can confirm that the part number I used fitted fine. :driving:
 
GreyZed said:
Just in case anyone else has a similar issue I thought I'd report back on this issue.
Click to expand...

Well done & thanks. Very thoughtful and useful information. Glad its sorted :thumbsup:
 
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