Z4-forum.com

Hey guys,

My zed is running great apart from a slight hesitation at very low revs under load - usually 1-2k rpm and when in a higher gear.

No fault codes come up (although that’s only using cheap scanner) and no warning lights. I’ve also noticed the car popping and crackling a bit more -(not that I’m complaining!) just wondered if it’s all linked - maybe a spark plug not burning fuel properly then dumping into exhaust?

I’ve searched the forum and read about coil plugs etc but without a fault code is there much I can do?

oh and I've cleaned my MAF using electrical contact cleaner and no visible air leaks

I know you guys like pictures so here’s my zed in Pembrokeshire

That is classic worn spark plug symptoms.

Great - cheap fix hopefully! Confused by which plugs to get ecp comes up with a few options - will they all fit? Currently between these

https://www.eurocarparts.com/ecp/c/BMW_ ... fdb&000301

Or these

https://www.eurocarparts.com/ecp/c/BMW_ ... 94b&000301

chrisgreen wrote: ↑Wed Dec 06, 2017 7:20 pm Great - cheap fix hopefully! Confused by which plugs to get ecp comes up with a few options - will they all fit? Currently between these

https://www.eurocarparts.com/ecp/c/BMW_ ... fdb&000301

Or these

https://www.eurocarparts.com/ecp/c/BMW_ ... 94b&000301

The single electrode iridium is the one to go for (your second link) but don't pay £16 ech!!! £5 ech (for 6) at Opie oils... https://www.opieoils.co.uk/pv-214128-bo ... ingle.aspx

Thanks - all changed - did it on my lunch break and was surprisingly easy! Was still on original plugs so definitely needed doing!

Hmm problem still persists - it’s only over half throttle in higher gears at low revs. What else could it be? Fuel pump? Assume if it’s ignition coil there would be a misfire or some sort(which there isn’t)

Hmmm, well sounds like they needed changing anyway so no loss. WOT (max torque point) puts maximum stress on the electrical system so I'd probably be changing coils if it were me. It's all guesswork without codes / live data.

If not coils, lamba sensor maybe? The lambda is ignored at WOT but there could be a lazy signal during the transition.

If the spark plugs are original, what else has been neglected from the service schedule? Assuming air filter is clean? Other common problem areas are a split in the elbow on the air intake, crankcase ventilation valve, VANOS seals and of course the DISA.

Finally, did any of this coincide with spraying your MAF with electrical contact cleaner by any chance? Just that some cleaners leave an oily film to subdue arcing which could screw up the MAF. Carb cleaner is generally a better thing to use.

Yea I thought coils - won’t they throw up a code though? Again without live diagnostics don’t want to be changing all 6! I did the hand over oil cap test for Ccv and vacuum seemed to be ok - and only cleaned the maf after it started happening!

Thanks for your help - I’ve got it booked in with a specialist so hopefully get some live codes and readings going!

Would be much easier if it just threw up a fault code!

chrisgreen wrote: ↑Thu Dec 07, 2017 6:17 pm Would be much easier if it just threw up a fault code!

Indeed it would. You sometimes get 'soft codes' stored which don't bring the check engine light on. Coils can fail in different ways and don't always die completely. Let us know how you get on.

ph001 wrote: ↑Thu Dec 07, 2017 6:57 pm

chrisgreen wrote: ↑Thu Dec 07, 2017 6:17 pm Would be much easier if it just threw up a fault code!

Indeed it would. You sometimes get 'soft codes' stored which don't bring the check engine light on. Coils can fail in different ways and don't always die completely. Let us know how you get on.

And as if by magic managed to get the check engine light to come on! It went off again but there’s a now a fault stored - P0305 which I believe is cylinder 5. I shall swap that coil over to number 4 just to double check it then il get a new one!

Although seems strange it came on after I changed the plugs - there’s no ‘incorrect’ way of installing them? I hand tightened them then did Half turn as didn’t have a torque wrench.

Was gonna say as soon as I saw this it's classic coil pack failure symptoms this. They only fit one way

chrisgreen wrote: ↑Thu Dec 07, 2017 7:18 pm Although seems strange it came on after I changed the plugs - there’s no ‘incorrect’ way of installing them? I hand tightened them then did Half turn as didn’t have a torque wrench.

Nah, can’t get it wrong, just the fact that you have disturbed an already dodgy coil pack. The others probably won’t be far behind. Change all 6 for Bosch parts and be done with it.

Thanks - is it common for these coils to go? Read somewhere that it’s fairly uncommon on m54?

chrisgreen wrote: ↑Thu Dec 07, 2017 10:28 pm Thanks - is it common for these coils to go? Read somewhere that it’s fairly uncommon on m54?

All cars are common for coil packs from the early naughties from my experience tbh.