Very loud bang followed by limp home mode

[Jsd]

As the title suggests really, i know without actually looking at the car no one will be able to tell me exactly whats wrong. I'm gonna get it trailerd to the dealership tomorrow.

The car said drivetrain malfunction but its changing through gears 1-4 just fine (i wasn't prepared to put my foot down enough to check all gears) its running pretty rough and I'm wondering if I've blown a piston somehow?

when driving back, letting the car coast downhill every now and then i would get more loud pops and bangs...these did not sound like normal backfires.

Its dark out so i can't see if it was smoking out the back but it stinks of fuel.

blown turbo maybe?

any thoughts much appreciated

[BMWRog]

Not got any ideas other than what you've mentioned. I feel your pain bro... Is it still under BMW warranty?

[Jsd]

Originally Posted by BMWRog

Not got any ideas other than what you've mentioned. I feel your pain bro... Is it still under BMW warranty?

warranty expired last month

most expensive sound I've heard in my life thats for sure.

[Jsd]

So thinking about this more, a loud bang followed by a misfire and strong smell of fuel is for sure going to be a blown piston/cylinder..at least.

does anyone know what the sort of repair for that would be if i was lucky enough not to have anything else damaged? is it new engine territory? i have no idea how much that would cost :/

[BMWRog]

I'd certainly not disagree with you re possible damaged piston. If that was the case, you'd be extremely lucky if it didn't damage the cylinder bore, and the head as well. A compression test will probably be the first step.

Couple of years back I had a new block and pistons on a 645, fortunately under full BMW warranty. The guy at the dealership told me I'd have been looking at around £11K if it was coming out of my pocket. I'd say an M6 will undoubtedly be more...

[gregmb]

If it was your factory warranty that just expired last month, then I would explore a goodwill fix with the dealer. There a chance the the service manager can persuade BMW to cover part/all of the repair, especially if you have a relationship with the dealer. It's probably worth exploring under the circumstances. Your odds are probably better if you haven't modded the engine as well. Good luck and hope it works out.

[M60]

I had what you experienced on my s85 m6, an yes it turned out to be an injector stuck open.. Flooded the bore bent the rod an caused bore scoring aka new engine, I really hope that's not the case for you and don't want to worry you off course but it does sound very similar to my situation 6 months ago.

As said contact customer services and good will department an put your case forward, get a compression test done ASAP as BMW will want to strip it just to tell you it's broken when they can tell you via a bore camera an compression test instead of charging you £4000 just to tell you it's broken.

[Jsd]

Thanks for the responses guys

unfortunately i have no hope of a good will gesture, the warranty wasn't renewed because the car has now got catless DP's and been remapped - The dealership knows this too- i expect them to give me the "well what did you expect would happen" conversation.

I should have a better idea of the problem by tuesday. The only piece of optimism i have is the car needed to be started briefly to get it on the trailer and the guy driving the truck said apart from the misfire it sounds ok - no bangs or rattles, no black or white smoke so may get lucky. He reckons if it was catastrophic damage it would be clattering and all sorts.

will have to see what happens but not knowing for a few days is frustrating!

[G3t0ut]

I hope for the best for you. fingers crossed

[mastatikle]

How many miles are you at?

[Jsd]

Currently at 41k miles.

Had an update - it doesn't appear to be as bad as i first thought. Fuel injector failure has then cascaded causing all other injectors to fail on bank 1.

Other than this, there doesn't seem to be any mechanical damage to the engine and no other fault codes present. No metal shavings in the sump etc and they suspect the loud bang was unburned fuel detonating.

They are going to change the plugs and injectors on the bank and do an oil change before they can carry out final tests. Fingers crossed, that should be it.

This task is already going to cost me over £2k so i don't want to incur any unnecessary costs, but do you think it would be worth replacing plugs and injectors on the other bank as a precautionary measure?

[M60]

Injectors are not a service item so don't need to all be changed as they can last forever and don't have a set lifespan however BMW "recommends" you change all in this situation.. I wouldn't change them all due to 1 faulty injector However plugs I would change all at the same time and I would give the injectors an ultrasonic clean an test just to be on safe side which costs about £150 in total vs £100+ for each one to buy new

Instead of all that money spent a best check would be a simple compression test for £100, that way your not wasting money on injectors an other bits if the compression test immediately reveals your down by 50psi on cylinder 5 etc.

[Jsd]

Originally Posted by M60

Injectors are not a service item so don't need to all be changed as they can last forever and don't have a set lifespan however BMW "recommends" you change all in this situation.. I wouldn't change them all due to 1 faulty injector However plugs I would change all at the same time and I would give the injectors an ultrasonic clean an test just to be on safe side which costs about £150 in total vs £100+ for each one to buy new

Instead of all that money spent a best check would be a simple compression test for £100, that way your not wasting money on injectors an other bits if the compression test immediately reveals your down by 50psi on cylinder 5 etc.

Thanks for this.

I have called and requested they do a compression test before fitting the new parts to which they have agreed - won't charge me any more to do this as the plugs etc will be coming out anyway.

They did mention on the phone that no compression faults were present so, whilst they can't absolutely guarantee it, they are fairly confident there shouldn't be any compression issues.

My sphincter continues to twitch...

[M60]

Originally Posted by Jsd

Thanks for this.

I have called and requested they do a compression test before fitting the new parts to which they have agreed - won't charge me any more to do this as the plugs etc will be coming out anyway.

They did mention on the phone that no compression faults were present so, whilst they can't absolutely guarantee it, they are fairly confident there shouldn't be any compression issues.

My sphincter continues to twitch...

No problem.. It's better to be safe then sorry and as you said the plugs are already out, plus to my knowledge the idrive/ecu can not detect compression faults and raise it as one.. It would just raise it as misfire codes, present with possible coughing spluttering, smoke etc.

Once the test is out the way it's all guaranteed and you know whre you stand.

[mastatikle]

What do you think was the root of this? I want to tune my car with down pipes but I'd be nervous of something like this happening. I'm at 42k miles with no performance mods other than exhaust:

[Jsd]

Originally Posted by mastatikle

What do you think was the root of this? I want to tune my car with down pipes but I'd be nervous of something like this happening. I'm at 42k miles with no performance mods other than exhaust:

I'm not entirely sure but i'm keen to find out. Fuel injector failures are commonly reported online for a range of BMW models across the last 2 generations -search google. Although i expect the % of failures vs number of vehicles produced is very low I would consider it a 'known' problem.

My car has had a stage 2 remap from Evolve and produces 750hp. I would highly doubt these modifications would have influenced this failure, especially considering the large number of injector failures that have occurred on standard cars. As far as i'm aware the injectors for the M6 are not specific to the model and are used in many other series.

I wouldn't expect reliability to be affected much if the car is well maintained and has been tuned by a tried, tested and reputable tuner to a moderate level. Just bear in mind if you wind it up too much things will inevitably start to go bang.

The one thing you DO need to take into consideration is your ability to get a warranty on the vehicle after it has been modified. I would have renewed my BMW extended warranty last month if they would have let me, and this issue would have been covered under it.

[Jsd]

Quick update for those interested;

BMW have completed a compression test and this came back fine. New injectors plugs and oil installed. Car has been run at idle without any issues and they are fairly confident there shouldn't be any further issues.

Their prognosis was injector 4 overfuelled and 'failed' (stuck open or closed i dont know). This for some reason caused all the others on the bank to fail too.

They are keeping the car over night and will road test tomorrow, checking the oil for contaminants once its been run.

hopefully they will be able to give me probable causes and more information tomorrow.

[M60]

That's brilliant news! It would have stuck closed which would just shut the bank down for safety an then you'd feel like your driving a 2 litre single turbo lol.. Stayed open an you'd have a £35,000 bill, (mine was £46,000 on the v10) once they are stuck open they don't stop throwing fuel in to the cylinder.. Mine emptied £20 of fuel in 1 mile lol which even for an s85 is pretty bad before setting my rear bumper on fire too haha.. Was a bad night that ended good in the end from BMW warrenty.

[Taheemr]

£46k for the V10 Engine, the car would surely be beyond economical repair for that figure ?

[M60]

Originally Posted by Taheemr

£46k for the V10 Engine, the car would surely be beyond economical repair for that figure ?

That was the engine for approx 32k, £4.5k to diagnose the original engine, 6k worth of cats (raw fuel destroys them) labour, bits bobs oils, so yep £46k

BMW warrenty would only pay a maximum claim up to the value of the car which at the time was 22k and they wanted me to pay the rest as part of there terms an conditions, it got a bit messy, many letters were written but with good backing from my local dealership an involving financial ombudsman they eventually agreed to pay me out a settlement of the 22k in cash to get the car repaired elsewhere "as a goodwill gesture".. so I immediately sold it with no engine for 12k plus the 22k they paid me I walked away very happy in the end.

[Bimmma]

I had a similar injector failure with it being stuck open and even had fuel in tailpipes. Fortunately I was still under warranty so I got them to change all the injectors, plugs and coils. There were multiple misfires on bank 1 because of the fail injector. No internal damages, compression and leak down tests were all good. I know of a another local case with a similar injector failure. Seems like injector issues are not that uncommon.

[M60]

Originally Posted by Bimmma

I had a similar injector failure with it being stuck open and even had fuel in tailpipes. Fortunately I was still under warranty so I got them to change all the injectors, plugs and coils. There were multiple misfires on bank 1 because of the fail injector. No internal damages, compression and leak down tests were all good. I know of a another local case with a similar injector failure. Seems like injector issues are not that uncommon.

You was VERY lucky as open injectors left to do there thing I,e engine hydrolock is sure certain death for any engine, mine took just a few minutes and my oil, coolant, was filled with fuel not to mention what it did to the cylinder walls an rod.

I think injector issues on bmw's are more common then people make out but not everyone shares there story online, I didn't think it would be an issue on the f series though which is quite surprising but I'm under warrenty so I don't mind for now.