[firedragon]

Hello All,

I am new to BMW's and need some help and assistance with a bad misfire issue that has come out of nowhere.

Some history: I had a service from an independent garage that I know well last weekend [Saturday] and they changed all 6 spark plugs as well as oil and filters etc. All was well.

On Wednesday I ran the petrol tank down to --- on the clock [not intentional to get that low just caught out on the motorway], probably took it down to -3 miles. Anyway, filled up the tank at a Morrisons and went on my way. 5 minutes back down the motorway and the car started to hesitate on acceleration and then it misfired and then ran on 5 cylinders with the EM light on.

Took it straight to the garage that done the service as thought it was a plug issue. They done a diagnostic and it stated a misfire in cylinder 5. They proceeded to swap the plug for another, reset the codes and ran the car, the EM light come on again. This time it stated cylinder 2 was misfiring. They then swopped over the coil from cylinder 2 with 1 and swopped the plug from 6 etc to eliminate any plug or coil issue. Reset again, ran the car and the EM light came on again - still referencing cylinder misfire.

They assured they torqued the bolts to the correct setting so no combustion gas is leaking out and that the coils have been seated properly - this I have double checked.

I cannot understand why the misfire went from cylinder 5 to cylinder 1 when all the plugs and coils are ok? Furthermore, one may think the culprit could be a clogged injector from some dodgy fuel but again would this not be consistent to one cylinder or several/all - why effect one then another with the original cylinder effected now ok..?

I have had a very low battery warning since buying the car some eight months ago and have just replaced the battery for new yesterday. This was replaced after the misfire issues.

After reading many posts it would seem that most people have a consistent cylinder down whereas I have had one and then it moved to another and is now consistent to that cylinder - electrical issue maybe, however all wiring to the coils seem ok.

Some people say that the low battery voltage can mess around with the electrical system and this could have spiked the ECU/DME and hence causing the strange misfire.

Others say that when the plugs are changed the ECU needs to be reprogrammed i.e to reset the adaption module - I thought though that this adaption module reprograms itself to ensure the right spark across the plugs etc.

Basically, now I am getting nowhere with the garage that done the service of which I think they are probably not at fault anyway, and the stealership are quoting £216 to just have a look for 2 hours

The car is now un-driveable and sounds like a Citroen 2CV with BMW not able to look at it for another two weeks. To boot I will probably have to get it put on a flat bed to get it o the garage...another load of cash.

Do you think it is ok to drive to the garage i.e. will the ECU have closed down the injector to the effected cylinder to prevent CAT damage?

Apologies for the lengthy post.

Any advice would be more than welcome and thanks in advance for reading this long thread.

Thanks

[KM79]

Were the spark plugs genuine items?
Did the misfire move to a cylinder that had parts transplanted to it?

[firedragon]

Hi mate, thanks for the reply.

The plugs were NGK not Bosch but they are listed as compatible according to the mechanic that fitted them.

Yes, I think you maybe right. I think we swopped the plug from 5 to 2 originally but did try other positions too after. Why, what you thinking?

[old grey steve]

Could be a number of issues unfortunately running one if these low on fuel's not a smart move (though as you say it wasn't intentional if you see your tanks reading 25% full I'd be ready to fill up I've always adopted this policy)you can create issues re the Nix Oxide Sensor and at £305 odd plus VAT it's a costly error, when these things take place we can actually ascertain why/whether a fault/or failed sensor and a lot if the time we see poor fuel quality as the end result. When asked we see some repetitive answers namely 95 RON Supermarket fuel around our area (Hertfordshire)all we can find is advise and educate the customer that in occasions fuel isn't just fuel the cats react to it.

Your cars drawn low on fuel you'll find the pumps are sucking for fuel that wasn't there then sadly as you've discovered there's been a hiccup with the fuel I'm betting the above comment I've made re poor quality fuel has partially been the issue.

The misfire could also be down to a failing low pressure sensor common as anything they seem to create slightly different end results but can play havoc and think about it you were low re fuel so I'd look here as this would of come in to play. Although you've hit a Poitier re misfire why is it misfiring if the garage your cars with a struggling beyond the coils/plugs logic says they need to have a look upstream and I'd bet somewhere in their low pressure sensor will figure.

Also on my mind is a possible pump fault due to dragging low fuel did you hear any noises?

Cylinder misfire if looked at say on a SnapOn machine or something like this dan give you a bum steer sounds like the garage has fop done all the basics if you have the option of finding a decent Indy with Autologic I bet you'll find the answer to your problem fairly quickly. And it's fuel related to. Plugs and coils are contributing to the burn if that fuel if it's poor then they'll throw their toys out if the pram too.

If only you were local to me(Stevenage Herts)as we like a challenge.

Hope it all works out. But get the low pressure system Sussex out I'd get rid of that fuel too to be 100% safe(sounds way OTT)but crap fuel can play havoc. I'd fret some decent Super-unleaded fuel also a decent commercial fuel additive like Forte or TunAp(won't find thus in Halfrauds I'm afraid)and move on.
Injectors could shut down if told to do so to self protect again if Autologics used there's scope to view if they have shut down why. Also after an event like this look at sorting the fuel filter out too just to be safe.

Just on the subject of plugs on Wednesday I noted mine was down on power had them in for 8 or so days when removed we found 3 actually had cracked ceramic coatings 2 of which we could spin around and move up and down and they showed as a result arcing signs. Scary yet I had no misfire just a reduction in power

Steve

[firedragon]

I think we have eliminated it being a plug issue but you have me thinking now.

Do you think these NGK plugs could be an issue?

Also, if the misfire has shut down the injector in cylinder 2 how can you reset this so the injectors starts working again - a static ECU reset or will it have to be done by diagnostic computer?

The reason I ask is that surely if the injector has been shut down a diagnostic will always pick up a cylinder misfire and thus whatever plug is put in that cylinder it will always misfire...correct...?

Do you think it has anything to do with a blocked injector due to crap being picked up from the tank - although one would assume the fuel filter would prevent this?

[firedragon]

Thanks for your comments too 'Old Grey Steve', yes, if you were closer I'd be straight over to you.

It just seems very coincidental that the hesitation and then misfire started straight after putting the fuel in from the Morrison Store. It could be pure coincidence but I reckon it is possible the fuel is contaminated. How is it best to drain the tank, syphon off?

One thing I think I haven.t mentioned is that the car has been confusing itself when going down steeper hills. It seems to rev up in a higher gear until it sorts itself out.

Steve - do you think it is also a possibility that the low battery could have played havoc on the electrical system and spiked the ECU or are we truly looking at a fuel issues.

Lastly, what is the function of a Nix Oxide Sensor as never heard of this...where is it too?

Cheers for your help

[old grey steve]

Originally Posted by firedragon

Thanks for your comments too 'Old Grey Steve', yes, if you were closer I'd be straight over to you.

It just seems very coincidental that the hesitation and then misfire started straight after putting the fuel in from the Morrison Store. It could be pure coincidence but I reckon it is possible the fuel is contaminated. How is it best to drain the tank, syphon off?

One thing I think I haven.t mentioned is that the car has been confusing itself when going down steeper hills. It seems to rev up in a higher gear until it sorts itself out.

Steve - do you think it is also a possibility that the low battery could have played havoc on the electrical system and spiked the ECU or are we truly looking at a fuel issues.

Lastly, what is the function of a Nix Oxide Sensor as never heard of this...where is it too?

Cheers for your help

Fuel wise the tank was low way too low then filled up IMO the cars reacted to this I suspect low pressure sensor but of course there could be something else, running it low I suspect Nix Oxide faults to be present coupled with fuel quality(which may be a coincidence)but we've seen enough Supermarket fuel issues as I've said to warrant me advising customers to use decent Super Unleaded fuel from the big players.

If you need to drain the tank it's a rear seat out job same procedure we tackle when a cars been misfueled.

Battery wise they are IMO good for around 4 to 6 years on the later cars with EfficientDynamics we've via diagnostic exhausted battery faults in around 3 to 4 years. We check to see the charge data anything below say 66% on our diagnostic machine can pull data indicating exhausted battery and every now and again you'll see the battery light on the dash. Symptoms of the battery issue sadly vary, from losing the clock resetting all radio station data or losing it to suddenly finding your cars rear screen heater or heated door mirrors don't work. When the battery gets critical the car effectually shuts down unnecessary control units to conserve power to enable the car to function and drive.

Therefore although an annoyance once a new battery is installed, via diagnostic you need to have the battery sync'd to the car you can resurrect full power status and can re enable all system and get everything working as they should as they've effectively hibernated or closed down.

You can drop in to Halfords and get a battery fitted but you'll have issues due to the fact that the car needs to be instructed that it has a new power supply has been installed and a basic set up initialisation sequence is ideally required.

Until told otherwise the new battery will function, but won't function as it should hence the need to sadly go through this process otherwise with a new battery fitted the car will still hold power faults and will react in the same way until its memory regarding power faults have been sorted. We've see a fair few cars with power issues that other garages have fitted batteries too only yo find the battery's fine but everything requires setting up.

On the downhill thing I'm guessing yours is an Auto? Fairly normal. Though again fitting a new battery us going to be a good thing as everything's fed by power and a poor supply won't help if yours is an Auto(only guessing) then control units may have power supply under voltage/over voltage faults applied.

Your Nix Oxide Sensor is a high temp ceramic sensor with a built in control unit that's there to detect Nix Oxide content after burn(measured in ppm)parts per million. Anything outside the permitted range will create a fault to my eyes they are very sensitive but they are an emission control device that's here to stay unfortunately. There's a science behind it but basically it needs to function correctly and tondo so everything has to be yo the cars liking therefore decent fuel, keep the tank topped off will help keep this sensor on the ste sight and narrow.

Hope this helps a bit

[KM79]

You say NGK plugs?Im almost certain that the alternative to the oem Bosch is not a multiple prong design and was never intended for the n54.It can be used although it must be gapped correctly as it's a single electrode type.
If the cylinder misfire moved when you changed things around it had to be the component you moved ie plug/coil.My money's on a bad plug or as I say incorrect/ not gapped type.
Some good info from Steve all except the Nox sensor.The N54 doesn't run in stratified lean burn so doesn't have one fitted.

[old grey steve]

Originally Posted by KrisM79

Some good info from Steve all except the Nox sensor.The N54 doesn't run in stratified lean burn so doesn't have one fitted.

Ta and oh shit yer right I've got Nox on the brain as we've done shed loads on 325/330's but yer right our 335i's run a set of Lamda's 4 in total and 2 per manifold, 2 or which are regulating units pre CAT and the other 2 are post CAT(primary in the down pipe)these will pick up the burn info and adjust accordingly and when you have a map done with DeCatted pipes unless you take into consideration that the CATS been removed these little buggers will throw the EML on.

Re the plugs I'm safely back on BMW supplied Bosch items when my walnut blasting was done at the last minute I chose to renew my plugs. Cross referencing the Bosch number I got a set of NGK's sent in the numbers tallied but they didn't exactly do me any favours as they fragmented in situ, I lost power and as I discovered when they were removed the ceramic coatings we're lose (you could spin them around with your fingers to an accompanying squeak)but these specific NGK's are the Bosch equivalent items. It's the first time on 135/335's we've used them just my luck they were duds, re installing the Bosch items bought full power back.

The fact that OP ran low on fuel filled up then picked misfire up upon leaving the petrol station to me has a whiff of that ole pressure sensor or something along those lines, could be wrong as plugs/coils can quite rightly produce all the misfires you can ever dream off. If available a smooth running check on all 6 cylinders would help(though unless you've bit a decent diagnostic machine it's difficult to do this)the garage OP put the car into sounds like they've done the basics re coil/plugs etc. injectors can play up too again smooth running check would drill this down as you could quickly move say coil 5 to coil 3 swap them around and re check the results if the values don't change but stay say on cylinder 5 look at doing the same re the plug(check the plush carefully when removed)run the sequence again and see if anything alters. But it sounds like perhaps this May by the garage OP's visited this may have been done already?

Plugs coils or fuel system related fault.... Guess until the cars looked at where specific info can be dialled into we'll just have to wait.

[lolololol]

Sounds like a gapping issue - NGK's need to gapped manually.

[Russbmw]

Just to be clear, there was no sign of any issues whatsoever until you ran the car dry, right?

[old grey steve]

Originally Posted by Russbmw

Just to be clear, there was no sign of any issues whatsoever until you ran the car dry, right?

that's how I read it Russ

[KM79]

Does seem coincidental,and I've wanted to blame fuel on many a job I've done but I would want to be having a close look at those plugs first.

[firedragon]

Evening All,

Thanks for all the further comments and suggestions, all of great help cheers.

Very interesting what is being said about NGK plugs...if the plug gapping was an issue would this not have happened straight after fitting and not three days later?

The plugs were not gapped as I saw them being straight in from the box...is it worth getting them out and gapping them or getting the garage to get OEM Bosch instead?

Russbmw - There has been no issues at all regarding misfires or hesitations etc until the car was filled up. Literally after 5 minutes or a few miles down the motorway after filling up the car started to slightly buck or hesitate on acceleration [like fuel starved] and then it misfired and EM light came on. Could well be a coincident like we all say but also wouldn't surprise me either as it has happened to others before - especially from supermarkets!

Do you guys think the car is safe to drive to the garage/stealership circa 6-8 miles or should I get it picked up?

[firedragon]

Also, when the misfire moved from cylinder 5 to 2 the mechanic then took out the new NGK plug, reset the EM logs and replaced it with one of the old OEM Bosch plugs...does this eliminate plug issues?

Side question - Would resetting the EM logs via diagnostic machine allow the system to reset a shut down injector [assume so] as I am concern that if the injector stays shutdown then any change to the plugs or coil would make no difference.

[KM79]

Once the knock system detects no misfires it will re engage the injector.Mixing plugs is a huge no no.is it currently running will all the same brand now?NGK need gapped,it has to be ruled out.Me personally I would junk them and get the Bosch ones.

[firedragon]

Cheers KrisM29 for the clarity on the injector reset.

The mech only put the old Bosch one back in to try and eliminate the NGK plug being the issue. All plugs are currently NGK's.

As before, would a plug gapping/brand issue not have caused an issue immediately rather than several days later?

[KM79]

Difficult to say,maybe by the time the adaptions have started to set in it's started misfiring.My car ran like sh*te after I changed the plugs( oem ) and it's only just settling down now a couple of thousand miles later!

[firedragon]

Did you have a misfire too or was it just sluggish and that?

Anyone else had issues with new plugs after several days rather than immediate?

[lolololol]

Pull the plugs and check all the gaps - have you done that ? That is the 1st place I would start personally. If they were fitted straight out of the box then that is an issue in itself !

[firedragon]

The mech said they were already pre gapped, hmmmm.

If not gapped correctly I would expect the system to flag this quicker than 3 days but I am no expert!

Is there anything that can delay the system picking it up and thus delaying the misfire?

I think I would rather check the gaps before shelling a load out to BMW. Trouble is that if it is not a gaping issue the mech will charge me again and I will still have to shell out with BMW anyway - suppose it is a process if elimination!!

Is gaping the plugs easy for a DIYer at home, if so how and where can I get the specialist plug tool to get the plugs out?

[KM79]

The thing with mine was I did a walnut clean,plugs,and reset all the adaptions at same time.It started to chug a bit at idle,but gave it an adaptions roadtest and it seemed to get better.Its never been the same since to be honest,but it's better when warmed up.It wasn't misfiring just a bit lumpy.

To gap the plugs you'll get a 3/8 socket off eBay for £7 and you'll need a set of feeler guages for a coupe of quid.

And those ngk's def aren't pre gapped as I looked into fitting these as an alternative to the Bosch ones as they're a stage colder plugs.the info I found on the net states they must be gapped as there originally an r56 Mini Cooper plug.