TangoVTEC

Really scratching my head on this one, so any help would be a godsend.

Car is a 2007 BMW 118i 2.0 litre direct injection petrol.

I needed to perform a compression test on it, as the owner wanted peace of mind whilst it was still under warranty.

I disconnected the injectors, removed the spark plugs and tested, all as normal. Readings are fine across all four cylinders.

Upon reinstalling all the bits, the car now runs like crap with just 2/3 cylinders working.

I've done many a spark plug change and compression test and never had this.

I managed to do a few basic tests before it got dark (and extremely cold!) and I've found the engine is non-reactive to coil packs 1 and 3 being disconnected, so you'd think that it was either those coil packs or the plugs below them that are at fault. But no, when the plug was removed from the head and placed into the connected coil pack there is a spark from both?!?

Fuel injector issue? Do they not like being unplugged?

arsie

Sorry can't help you need to get on the BMW forums and ask and/or get to a good Indy BMW mech near you.

There is lots on Youtube e.g.
Could be a tip on that vid or others to help you?

Nottm_S2

Coils are notoriously fragile on these i think.

you need to read the codes then swap coils/plugs around and see if the issue moves i think?

does it stink of fuel?

Nick Graves

Do you need to introduce the coil packs to the CAN bus?

Sounds a bit crap...

gaddafi

Check for air leaks around any trunking you've removed, especially anything around the MAF

Is there an IACV - have you reconnected?

Would be some coincidence for two coil packs to fail when you carried out your inspection

TangoVTEC

Well, after a long, confusing and somewhat expensive day it appears that the process of removing plugs, compression testing and re-fitting was all too much for the solidity that is 'German build quality' and saw off at least one spark plug, one coil pack and one injector!

Believe me, I'm not a heavy handed oaf, I was a VAG trained technician back in the day (and they make some flimsy electrical stuff - or certainly used to!) and have been working on cars for a good few years now and have never seen this!

My crumb of comfort in all this is that t'internet is awash with these kind of stories (wish I'd read em first!) and as has been said on here, they are a known weakness on these direct injection Beemers. There has even been a 'Product Enhancement programme' whereby they have a policy to replace the spark plug, coil pack and injector as routine on any misfiring cylinders. Just a mere £400 per pot in parts of course.

Sadly the car in question had to go away on an AA truck without me fixing it fully due to injectors requiring coding to the DMS (which I don't currently have the equipment to do).

On the plus side, I learnt a little more about the fragility of Bosch components, the lies and fantastically unhelpful, absurdly expensive behaviour of BMW main dealers (no, this is not something we commonly see.....) and I've gained even more appreciation for Japanese cars, and especially my Honda's which are beautifully engineered compared to this Deutsch twaddle.

Thanks to everyone for offering advice and info!

Nottm_S2

Shame.

None of those parts are BMW but what pisses me off most is the UK premium.

i imported my coilpacks for the S2 for a fraction of the UK price.

I guess coilpacks have much increased longevity over single coils and HT leads, my unmolested 2001 runs its original stuff.

s2konroids can do some bmw coding

Nick Graves

No - thank you!

Your experience may have saved a few people (though brand snobs probably won't be told) that this German stuff is utter shite. WHY does a fuel injector NEED to be introduced to a CAN? It's a solenoid and pintle, FFS!

The fact that Bosch, etc, have got away with sub-standard coil packs for DECADES mean they deserve to go bust. As did British Leyland in the old free-market economy days.

Denso FTW!

Do JLR use good ol' Merkin ones? It'd be a bit bloody ironic if the rump of BL actually uses half-decent stuff these days...

m1bjr

FWIW also:
If you change out the plugs and/or coilpacks on modern BMWs you MUST reset the adaptations.
This is even after coding new injectors or whatever else you did.
Also check the plug gap is what it says, even pre-gapped new plugs have been wrong - seen loads.
You need a BT or dealer tool to reset the LVS Values, this is a reset that has to be run after changing plugs or coils. (Adaptation of stratification).
It should be better right off the bat - but will improve more as the ECU re-learns.
There are complex algorithms used that allow for changing plug gaps and cylinder burn over time/wear etc.

As for fragility of parts? I don't see it.
Its quite common for people not to correctly hook up the coilpacks, I have done it myself.
Or they grease the plug threads or caps... another bad move.
Steve (ex 335i enthusiast and tuner)

gaddafi

I may be about to encounter this coding cobblers as I have to change some parts on an 08 beemer.

Seems little more than a racket to tie people to main agents. So much for the EU protecting consumers' interests.