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Discussion Starter · #1 ·
Really at wits end with my 2011 R56 Cooper S. It's been experiencing a very sporadic misfire issue. It's happened about 6/7 times now in the past 8 months and every time it has been after 1 hour of motorway driving, constant speed 70mph and only once after 20 mins (still motorway driving).

-P0300 code comes up showing multiple/general misfires and no other codes. Half engine light, limp mode, turns on with sluggish reduced power. Code repeats until engine is shut off.
-One time after fault I left engine off for 30 mins, it stopped faulting and got me 200 miles to my destination with no issues. Other times I've left engine off 24 hours and still faulting.
-Been in with a trusted Mini specialist 3 times who have checked/replaced sparkplugs, coils and software update. Unable to get it to fault whilst in the garage. Recommended I take it to main dealer for possible injector cleaning referencing PUMA measure 60055462-04 and thermostat check referencing PUMA measure 43562064-31.
-Main dealer (Haliwell Jones) took no interest in previous diagnosis. Assured me it was two bad coils, £300 replaced them and still faulted week after. (Also in health check they found exhaust flexi pipe to be leaking slightly, claimed it wouldn't cause the misfiring)
-Second visit to them diagnosed a new timing chain to the tune of £1300. "Carried out quick test and found faults stored for misfire, faults are being logged during crankshaft working cycle when cylinders are retarded compared to other cylinders, this is due to engine timing chain requires replacing." But also in their report... "Engine noisy replace timing chain and reassess for misfire issue".
-Wasn't convinced this is the fault, went for second opinion on the timing chain at mini specialist. They removed rocker cover, connected timing tools up and found the timing was spot on, no need for replacement.
-Car is now back at Halliwell but they're struggling as they can't get it to misfire for their investigation.
-Note: It had new timing chain tensioner and drive belt 2018 and HP fuel pump 2019. New plugs and coils 2021.

Really struggling with this as I can't rely on the car anymore and can't get the vehicle to fault for garage investigation. If the main dealer can't even figure it out I don't see a way forward without spending £,000's guessing what is broke and replacing everything.

Has anyone experienced similar issues that could shed some light on how they managed to fix?
 

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if were in front of me I would suspect deeper than just chain , ie valves are carboned up its bang on age and miles for this, stem seals go hard leak oil on rear of valves and hold valves intermittently off valve seats ,, pull exhaust manifold and inlet manifold off and put compressed air in each cylinder with all 4 valves closed and spray wd40 on rear of valves though the ports any bubbles needs a engine refresh ,,, would also add worth changing the crap flexi rings with 3 piece solid type so much better , sorts the crankcase heavy breathing and oil use . link below worth a read
will add they all go this way and all do intermittent misfires ,,, before spending anymore money in parts you really need to do the above rule it out ,, I would say out of 10 like this 7 are the above ,
also clear up about the flexi just after cat yes if leaking it will back suck on over run 02 on to the post cat 02 sensor and cause a fuel trim or sensor fault
 

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2011 Mini Cooper S
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Discussion Starter · #3 ·
if were in front of me I would suspect deeper than just chain , ie valves are carboned up its bang on age and miles for this, stem seals go hard leak oil on rear of valves and hold valves intermittently off valve seats ,, pull exhaust manifold and inlet manifold off and put compressed air in each cylinder with all 4 valves closed and spray wd40 on rear of valves though the ports any bubbles needs a engine refresh ,,, would also add worth changing the crap flexi rings with 3 piece solid type so much better , sorts the crankcase heavy breathing and oil use . link below worth a read
will add they all go this way and all do intermittent misfires ,,, before spending anymore money in parts you really need to do the above rule it out ,, I would say out of 10 like this 7 are the above ,
also clear up about the flexi just after cat yes if leaking it will back suck on over run 02 on to the post cat 02 sensor and cause a fuel trim or sensor fault
Appreciate your advice Mike might have saved us a lot of headache here, don't suppose you're based anywhere near Manchester to have a look?
 

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no mate sorry i'm way down Cornwall get the car to me I can have a look go from there with it, prob fit it in around working etc, most garage will crap them selves with such work as most will just want to stuff a recon motor in it if its that at fault and to be honest most are, realistically looking around a grand to refresh it maybe a tad more if needs a cat and 02 sensors,, and trouble with the cooper s if needs a cat they dont like running on the after market ones so would also need a ecu update that pulls the fault code that would appear from using a £200 cat rather than the £800 genuine one ,, that said if have no cat codes or 02 sensor codes at this point chance are it will play ok,, its strange one i have mot'd them and go thought 4hc and under 0.2CO after rebuilds and with the cheaper cats and the code that comes up i think the ecu expects to see higher emissions,
 

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2011 Mini Cooper S
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Discussion Starter · #5 ·
no mate sorry i'm way down Cornwall get the car to me I can have a look go from there with it, prob fit it in around working etc, most garage will crap them selves with such work as most will just want to stuff a recon motor in it if its that at fault and to be honest most are, realistically looking around a grand to refresh it maybe a tad more if needs a cat and 02 sensors,, and trouble with the cooper s if needs a cat they dont like running on the after market ones so would also need a ecu update that pulls the fault code that would appear from using a £200 cat rather than the £800 genuine one ,, that said if have no cat codes or 02 sensor codes at this point chance are it will play ok,, its strange one i have mot'd them and go thought 4hc and under 0.2CO after rebuilds and with the cheaper cats and the code that comes up i think the ecu expects to see higher emissions,
Just got off the phone with Halliwell I mentioned the stem seals to them but they said you would normally see things like consumption in oil, smoke in the exhaust and high emissions on MOT. I've had the car nearly a year now and keep checking the oil but never had to top it up it barely uses any, no visible smoke when faulting and passed MOT just last week. Is it still possible?

As usual they can't get the car to fault whilst it's been in their garage so they're sending me away again said come back when it's faulting so they can investigate.
 

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you sound like have a good one if no oil burning by now, then the other thing is inlet ports carbon up common repair is wallnut blasting , pull inlet and send a camera in have a look,
 
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