[Roadrebel]

Hi all

I've had this misfire for a while, when coasting into a roundabout then driving out it misfires quite badly until 2000 rpm then it goes as normal. I can get the eml to light up if I keep my foot down but if I nurse it through to 2000 it is ok.

Last week it advanced to a misfire on acceleration throughout the rev range with the eml coming on sometimes.

Took it to local indy who diagnosed faulty Nox sensor which was changed at great expense and guess what? It's just the same. It has made no difference whatsoever.

Diagnostics also came up with cylinder 6 misfire and aging cat. Next step is to change the coil pack on 6 and see what happens.

Any ideas or thoughts?

[therealdb1]

Fault codes: Don't you just love them?
If the mis-fire is only showing on cylinder 6 I would expect the problem to be specific to that cylinder and not a sensor that looks after a bank of cylinders. The finger is therefore pointing at a spark plug, coil pack or injector.
Easy job you can try before you spend more money is to swap the cylinder 6 coil pack with a cylinder from the front bank, say number 1 for simplicity. If the mis-fire transfers with the coil pack you can be certain you need a new one. If the mis-fire remains on number 6 do the same with the spark plug.
Technically you can do the same with the injector also but you will need to reprogramme the car at that point otherwise you will introduce other running issues as the DME has each injector's parameters programmed into it.
Let us know how you get on.

[Roadrebel]

Right, been back to the BMW indy today and they are saying that the cat is blocked and that is causing the bad running. I have excessive oil consumption (about 1500 miles per litre) which, they say, has caused the problem.

I am not entirely convinced.

[Chappers 71]

I wouldn't say 1 litre in 1500 was excessive, oil consumption is dependent upon driving style.

[therealdb1]

Originally Posted by Roadrebel

I am not entirely convinced.

I am not convinced either! If a cat is blocked you would not get full power once you clear 2000 rpm and it would not show a mis-fire on a single cylinder the whole bank would be affected.
Perhaps now is the time to seek a second opinion at another garage or grab some test gear and try what I suggested before.

[Dormermike]

Sounds more like a duff coil pack to me.

[Tr1ppy]

I think its either coil pack or injector. Failure of these components will cause errors to pop up for components downstream, especially the Nox sensor

[The0pportunist]

As others have pointed out, my money is on coil pack or injector.

[old grey steve]

If you've got a misfire type issue and previously you've had a Nox Sensor issue I'd be looking to do the following. I'd wager the Nox may have been corrupted by what I've written below.

I'd have the coils out and have the plugs out if the plugs are black or wet see if they smell a tad fueley if they do then chances are you have have an injector issue, also ask yourself a question when you start the car from cold does it run a tad rough for say a minute or so then seems to calm down a little? Reason I ask is if the injector(s) are playing up the injectors aren't regulating the fuel as required and issues arise where basically once the cars switched off there'll still be neat fuel being released by the affected injector(s) think dripping tap in a sink where the plugs left in and you'll get the picture, when the cars started the regulation of the injector(s) may already be compromised plus there's unburnt fuel sitting on to of the piston, the car can only burn so much fuel and essentially there's a possibility neat unburnt fuel been put through the exhaust system and this could possibly be the reason for the Nox issue thus corruption can occur, on the Nox depends on what faults were registered as there's up to 7 different registered faults re this sensor that can show up the faults registered on this can help ascertain perhaps why it's failed or faulty and this is what we look for as you've got to ask "why has it failed" not the fact that it has failed. On top of this if the plugs are black/wet another possible sign of what I've just said red looking at a fuel esq isdue more closely.

Seen over 40 N53's this year alone so far with this type of issue you can double check by scoping the cylinders(plugs out of course) using a bore scope camera one person presses the starter you observe the pattern then after a few seconds immediately switch off if you see fuel being sprayed after the event there's you answer(thing with doing this is you've got to be competent in looking for the symptoms and competent in knowing exactly what to do and if you're not DON'T attempt to do this test) if you see this type of issue long term best way forward is to hit all 6 injectors down side is they're not exactly cheap. If you can't afford to do 6 you'll ideally need to do 3 and you should put the beat of the current injectors on one bank and put say the new ones on another bank. However I've seen mid long term even doing this you'll end up at some point visiting the other 3 as long therm they usually have been compromised by past events. The main thing with injectors as I've seen they are not as easy to diagnose/spot as you'd believe and diagnostic smooth running results can sometimes just sometimes throw a red herring.

Plugs coils on their own yes can play up but on these cars as well to add to possible woes seen oil contamination on plugs/coils which can cause misfire issues too, usually either down to possible spilt on on top up(cylinder 2-3 misfire) or a rocker cover internal split causing oil to weep into plug wells (even see a bad cover contaminate an injector.

Best way forward as per opening statement pull coils/plugs inspect for colour and or contamination of plugs this will give you something visually at least to work from.

[Roadrebel]

Thank you all for your thoughts.

Old Grey Steve, I thought it was injector(s) leaking fuel into cylinder(s) when coasting and then trying to burn it off and mis-firing. It still does this. It didn't do it if I was poodling along with minimal throttle and then accelerated. I had already checked injector prices as I expected these to be at fault. I don't get the mis-fire at start up.

Now, it is fine at constant throttle at any speed but as soon as I accelerate I get a mis-fire. Bizarrely, if I plant the throttle to overtake, it changes down a couple of gears and flies past.

How long does it take to get at the coil packs and plugs?

I have worked on cars and bikes all my life but they seem so complicated these days.

Maybe I should take it somewhere for a second opinion, Any recommendations?

[Dormermike]

Misfire under load classic coil pack

[Roadrebel]

I think it would be a good idea to get a new coil pack on cylinder six. There are some on ebay for £20 new. They are Bosch so they should be ok or OEM?

[Dormermike]

Originally Posted by old grey steve

Seen over 40 N53's this year alone so far with this type of issue

Hi Steve. Are you seeing many repeat offenders these days or generally once these cars get index 11 latest injectors they are never seen again for that fault?

Thanks

[Dormermike]

Originally Posted by Roadrebel

I think it would be a good idea to get a new coil pack on cylinder six. There are some on ebay for £20 new. They are Bosch so they should be ok or OEM?

Personally I would just move it as someone else already suggested. Move to a different bank and see if fault follows.

[old grey steve]

Originally Posted by Dormermike

Misfire under load classic coil pack

This is not untrue hence perhaps the advise below can sometimes be a worth looking in to these engines do suffer coil/plug related issues but unlike this engine predecessor these engines also when people go for say a coil change sometimes come with a sting, hence my suggestion that pulling coils and plugs an inspecting isn't a bad move and if you see a black wet plug you know where you may stand. With these engines its something we go with rather than just the coil type option feasible where as with the older N52's resolving he issue is far more forgiving.

The suggested swapping coils over from say cylinder 6 to cylinder 1 to see if the fault transfers by doing this, is 100% worth doing as its straightforward to do and you can see immediately where it takes you and its true its not unheard of that this one single action can solve many an issue, but historically seen enough with more deep routed issues to say what I've said but IMO its worth checking.

Originally Posted by Roadrebel

I think it would be a good idea to get a new coil pack on cylinder six. There are some on ebay for £20 new. They are Bosch so they should be ok or OEM?

Its a cheap option and can indeed work I'd say like Dorermike's suggested if you are looking to see if there is a coil issue swapping to see if the fault moves from cylinder to cylinder would be a good call before opting to replace but I still maintain its worth checking the plugs to see if they are black/smell of fuel as it will help you build up a picture .

Originally Posted by Dormermike

Hi Steve. Are you seeing many repeat offenders these days or generally once these cars get index 11 latest injectors they are never seen again for that fault?

Thanks

The cars we have seen/are now seeing all come in with the same sort of symptoms and they vary re reported symptoms from a slightly uneven idle after starting to a hesitation/misfire type issue low down that can be driven through, classics thought would be as suggested following the coil/plug, fix but as we started seeing more and more of these cars with the same problems a picture starts to build and now when I book one of these cars in go through the diagnostic, checking plugs for any signs of fatigue, oil contamination, fuel contamination and coils for signs again of any contamination, arcing etc. And if I have reported to me a plug is black with one of these we suggest scoping injectors to see if any of weak, breaking down. It usually helps if its of any help if this test is done from a cold engine state.

When injectors have been removed replaced they are all the older spec injectors that have been removed. I'm not 100% sure how long the later spec injectors have been around for, but one 530i we did had injectors replaced in 2014 by a BMW dealer, car had done some big miles yet 4 years later 2 of them after scoping were suspect (one on each bank)and these looked like the later set up.But of the ones we have replaced I see a fair few back for servicing and have had zero issues.

Originally Posted by Dormer mike

Personally I would just move it as someone else already suggested. Move to a different bank and see if fault follows.

Yep not a bad move to start with

[Roadrebel]

Thanks for all the advice. I got P0306 on my iPhone gadget when the EML lit up on Saturday so it looks like I can easily see if the problem moves. When I get a spare day I'll go through it and report back.

[Roadrebel]

I had a few hours spare tonight so I took all the coils out. 2-5 were covered in oil, 1 had a little oil on it and 6 was dry. 6 and 1 both show signs of tracking through the rubber with 6 being the worst.

Obviously, I need to replace the valve cover gasket to stop the oil leak but I've cleaned up as much as I can and I'll put it back together and see what happens.

I can get 6 Bosch coils from Euro car parts for £113 with the discount if these are the problem so I may as well change them all.

[old grey steve]

Originally Posted by old grey steve

Plugs coils on their own yes can play up but on these cars as well to add to possible woes seen oil contamination on plugs/coils which can cause misfire issues too, usually either down to possible split on on top up(cylinder 2-3 misfire) or a rocker cover internal split causing oil to weep into plug wells (even see a bad cover contaminate an injector.

Best way forward as per opening statement pull coils/plugs inspect for colour and or contamination of plugs this will give you something visually at least to work from.

Originally Posted by Roadrebel

I had a few hours spare tonight so I took all the coils out. 2-5 were covered in oil, 1 had a little oil on it and 6 was dry. 6 and 1 both show signs of tracking through the rubber with 6 being the worst.

Obviously, I need to replace the valve cover gasket to stop the oil leak but I've cleaned up as much as I can and I'll put it back together and see what happens.

I can get 6 Bosch coils from Euro car parts for £113 with the discount if these are the problem so I may as well change them all.

Oil contamination isn't unheard of as I'd stated earlier(though these engines are far better re this issue than the N54's)the thing I'd say is though you've seen the condition of the gasket when the covers removed its 100% worth checking for signs of fatigue in the cover as a crack if there will create issues re loss of oil which will usually seep in to the plug wells, which you've kind of discovered, what you've got to still ask yourself is though you've inspected the coils and you've sen issues, replicating coils if compromised is the right way forward after say 100% dealing with the discovered issue re the rocker cover.

I've noticed you've not mentioned the plugs so far, I'd trust you'd be pulling these to inspect based on the fact that they'd of been compromised by what you've seen leaking from the rocker gasket, namely oil, I'd be wanting these out to have a good look for a few reasons which again I've highlighted on a previous post

As for my question which goes back to your opening post, if you've had a Nox sensor replaced was there a definite answer re why it was replaced? Now it could of been just the issue you've discovered where a certain percentage of the fuel delivered by the injectors wasn't being 100% burnt due to the issues the plugs have if that's the case then once all buttoned up the issues you've had may well be resolved my reservation is the amount of these cars Ive seen and the amount of people I've talked to who've gone through everything you've discovered only to find their cars still have an issue and when investigated further they've had the wonderful world of injector issues visit them a little later on.

What you've discovered, what you've seen and what you've stated on your opening post initially point to coils/plug type issue, which as Dormermike's stated is a classic issue, me being me, knowing these engines personally I buy this logic, but I'd still like to ask the question re the Nox replacement, which you highlighted, namely why it was replaced what were the symptoms, what faults were recorded on the fault reading that resulted in its replacement as if sulphurious was one of the faults seen 30EA then its worthy of a look re plugs and their condition.

[Roadrebel]

I put it back together without looking at the plugs just to see if I could put it down to the coil packs. The car is so much better now, I still get a misfire but nowhere near as bad and I haven't managed to get the EML to light up yet either. I was expecting P0306 to change to P0302.

Plugs out tomorrow I think and I will have a good look at the valve cover.

[old grey steve]

Originally Posted by Roadrebel

I put it back together without looking at the plugs just to see if I could put it down to the coil packs. The car is so much better now, I still get a misfire but nowhere near as bad and I haven't managed to get the EML to light up yet either. I was expecting P0306 to change to P0302.

Plugs out tomorrow I think and I will have a good look at the valve cover.

Good call and the right one best to check these things if it’s just oil contamination re the plugs/coils which you’ve seen then overall thought it’s a little costly to sort it’s a cheaper ending to your woes than the injector type issue

But all you can do is remove inspect and work from there

[Roadrebel]

It's been three days since I changed the plugs and coil packs and there is no hint of a mis-fire anymore. The engine has never run better and pulls strongly throughout the rev range.

The plugs were in a dreadful state with burnt insulators and huge gaps. Plug 6 had signs of tracking down the outside. I've never seen plugs so bad.

I found a crack in the valve cover which I have filled with epoxy for now.

Thank you all for your help.

[therealdb1]

Glad you have got it sorted!