[Dormermike]

hello

My n53 does mostly super short journeys and runs spot on.

As soon as i do a long trip though, say, going away for the weekend after about 30 minutes on the motorway i get misfires occasionally. Occasional meaning it'll glitch once or twice and stumble, usually at cruising rpm, very little power to accelerate through it, and is not constant requiring to pull over. it happens for about 10 minutes then stops and the engine runs spot on after that for the rest of the journey.

It is repeatable in the sense that the misfires happen at roughly the same point on the motorway. No DME codes, no lights on dash etc. Definitely misfire type thing though as the power drops slightly momentarily.

The wierd thing is on the return journey it never happens. That leads me to think its some sort of clearing out of the nox trap or something like that?

thanks!

[Phil325i]

I think you're probably right. I get something similar on long journeys. The car occasionally (in cruise) almost feels like it's running too lean and very slightly misfiring. No warning lights or error messages and otherwise runs fine. I've learned to live with it...

[Dormermike]

Thanks Phil. I know there is a parameter like 50mph and over half a tank of fuel. If im doing short journeys a lot i rarely hit that. So clearing out the nox stuff dors make sense.

Next up think ive got a touch of timing chain rattle on start up lol

[Phil325i]

Originally Posted by Dormermike

Next up think ive got a touch of timing chain rattle on start up lol

Interesting. I wonder sometimes if I have too, but it's only occasional and the N53 is a bit of a noisy engine! I'm tempted to fit a new tensioner, but genuine ones aren't cheap (about £65). According to RealOEM, BMW have redesigned it a couple of times so there might be an issue they've addressed which a new one would cure..?

[0l0dom0l0]

If you do have a bit of rattle on start up a new tensioner should fix it. They are activated by oil pressure and if the internal seals start to leak then they don't hold tension when the engine is switched off.

Re the misfires during regen I don't recall mine being too bad but if there are no codes then I wouldn't worry too much.

[bmwak]

Originally Posted by Phil325i

Interesting. I wonder sometimes if I have too, but it's only occasional and the N53 is a bit of a noisy engine! I'm tempted to fit a new tensioner, but genuine ones aren't cheap (about £65). According to RealOEM, BMW have redesigned it a couple of times so there might be an issue they've addressed which a new one would cure..?

I changed mine recently as I have been having a rattle on cold start (but now I think it is lifter tick). It was a waste of money to change. I have the new Genuine part and it was identical to the one removed. The new one is the modified part and old one was the original.

[Dormermike]

Originally Posted by bmwak

I changed mine recently as I have been having a rattle on cold start (but now I think it is lifter tick). It was a waste of money to change. I have the new Genuine part and it was identical to the one removed. The new one is the modified part and old one was the original.

If the new one was identical to the old one how could the new one be the modified part of the old one original? So there is no modification on the new part, you mean?


Re the rattle yes its on startup, i didnt think the n53 had the n43 timing chain issues but its a slip sort of sound, but crap for 75k. On my old m54 engine i took the tensioner out and stretched the spring myself, which quietened it down a bit.

Another place to look is the oil filler housing oil seal, i think it holds a volume/head of oil which may leak if the car is sat.

[Phil325i]

Originally Posted by Dormermike

If the new one was identical to the old one how could the new one be the modified part of the old one original? So there is no modification on the new part, you mean?

+1 It may have looked identical from the outside, but why would BMW issue a new part number if nothing had changed? Could be an internal improvement like strength of the internal spring, or an internal oil-way for example...

[bmwak]

Originally Posted by Dormermike

If the new one was identical to the old one how could the new one be the modified part of the old one original? So there is no modification on the new part, you mean?


Re the rattle yes its on startup, i didnt think the n53 had the n43 timing chain issues but its a slip sort of sound, but crap for 75k. On my old m54 engine i took the tensioner out and stretched the spring myself, which quietened it down a bit.

Another place to look is the oil filler housing oil seal, i think it holds a volume/head of oil which may leak if the car is sat.

The part numbers of both were marked on the piston and the original was definitely the factory fitted one and the new one was the supposedly revised part. Visually nothing looked different. Some people have mentioned that the piston is slightly longer and harder to compress, but I measured both and by pressing both pistons in and letting go they had the same tension.

I fitted a genuine BMW part too, not the 'OEM' specials.

[Dormermike]

Originally Posted by Phil325i

I think you're probably right. I get something similar on long journeys. The car occasionally (in cruise) almost feels like it's running too lean and very slightly misfiring. No warning lights or error messages and otherwise runs fine. I've learned to live with it...

Hi Phil just wondering if this was cured on your car since your n54 injectors went in? Just did a big trip in mine and sure enough car was misfiring randomly at around exactly the same stretch of motorway as it always does. Worse this time and passengers noticed. Once it cleared out, no issues. No codes or eml. Wierd.

[Phil325i]

Originally Posted by Dormermike

Hi Phil just wondering if this was cured on your car since your n54 injectors went in? Just did a big trip in mine and sure enough car was misfiring randomly at around exactly the same stretch of motorway as it always does. Worse this time and passengers noticed. Once it cleared out, no issues. No codes or eml. Wierd.

Hi. Can't say I've noticed this phenomenon for a while. Maybe the N54s have helped? I'm doing a long drive up north later this week - will keep my eye on it.

[Dormermike]

Thanks, be interested to hear either way. I'm doing loads of miles in mine at the moment and apart from misfiring / lean on that one stretch it's been flawless. It's returning expected mpg too etc.. only thing is exhaust seems a little sootier than usual but might be imagining that

[Phil325i]

Just returned from 450 mile round trip (on a single tank). Smooth as silk. No misfires, exhaust clean.

[Dormermike]

Thanks Phil. Sounds like I need to dig a bit deeper when I get back with mine

[Dormermike]

Does anyone know what might cause an occasional misfire and low power (meaning you have to change down through gearbox to power through it) but only at motorway speeds and only one direction - i.e. drive from cold a 30 mile journey. Misfire happens around 20 miles until 25 miles at motorway speeds only on the journey out. Leave the car at your destination, drive back eventually after a nice day out and engine is cold - no misfire. So only happens on outbound not return. I do this trip fairly frequently that's how I'm sure of the miles etc.

The car has no codes, just had a new battery as there was a code for that but it's made no difference.

New Delphi coil packs about 8 months ago to try and cure this, minor improvements maybe but not sure.

Car mostly does short trips and never misfires from cold though the index 11 injectors are probably 5+ years old at this stage so I'm wondering if they are in the way out.

Any ideas please ? Could it be NOx trap clearout misfires ? MOSFETs?

It's a 2012 n53 btw with an zf8 auto.

Thanks

[Phil325i]

Sounds like a NOx regen being carried out to me...

[Dormermike]

Originally Posted by Phil325i

Sounds like a NOx regen being carried out to me...

Yeah, I'd love to believe that, but I've had this car 7 years and I've never noticed this behaviour before. Exhaust is a little sootier than it used to be. I'm wondering if I'll be seeing cold start misfires come winter..

[Phil325i]

Originally Posted by Dormermike

Yeah, I'd love to believe that, but I've had this car 7 years and I've never noticed this behaviour before. Exhaust is a little sootier than it used to be. I'm wondering if I'll be seeing cold start misfires come winter..

Do you know an indy who has the genuine BMW test software (the one that works while the engine's running)? Might be worth getting a full diagnosis done. I've had this done a couple of times over the years to diagnose issues and each time it's come up trumps and highlighted the cause (which in both cases was not the cause I'd expected!).

[Dormermike]

Yeah not a bad shout actually. I have ISTA etc and could do live logging but if that fails I'll try an indy. I never use garages normally so didn't consider that tbh

[Dormermike]

Car had been sat laid up 10 days so i took it for a spin today - started on the button, no misfires at idle, left it idle for a minute or so, then took it on my usual route and no misfires there either. Weird. Not had a chance to get a garage involved but tbh i'm reluctant because its so hard to recreate - i'd need someone who REALLY knows this engine (more than i know it, and i consider myself pretty up to speed on them).

The fact it didn't miss or smoke on startup was encouraging, injectors must be OK, though i did smell something that sort of smelt like petrol in the exhaust but if that had been the case i'm sure it would have misfired.

Guess i'll just drive it and see if something develops.