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Discussion Starter #1
I recently bought an 05 plate Cooper S for my wife as our second car. It’s done 53500 genuine miles and is bodily in perfect condition ~ seriously like brand new! I knew it would need a new clutch and to rectify a steering cylinder leak, all of which has been done and she is running very smoothly...95% of the time! Every so often the engine warning light comes on and the car loses power almost exactly like “limp home” feature that I’ve experienced in other cars.....not sure if a Cooper S 15 years old has that? In any event the remedy is to switch off and restart the engine and it reverts to full power, again running beautifully. Three garages have been unable to diagnose/rectify the problem and this despite spending significant money on things like replacement plugs and ignition coil. Yesterday in the queue for car valet I was ahead of a home repair/servicing franchise van and he kindly linked me to his diagnostics iPad and it registered a misfire on cylinder 4 despite having the coil replaced last weekend. Suggesting just a loose connection and he having checked and tightened all of the them, I was anticipating no more trouble. Not to be.....the light suddenly came on on a journey today and the car lost power. I switched off and restarted and all was smooth on the journey home although the engine symbol light stayed on without any loss of performance.
I'm truly stumped....not a mechanic by any stretch of the imagination and now truly frustrated that I can’t rectify what must be a minor problem on an otherwise superb example of this iconic car. Can anyone help please?
 

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compression test number 4 first off,
as you have done plugs and coil pack hmm but i have seen brand new ones fail before,, injector problem would be my guess maybe stick injection cleaner through it, or remove fuel rail and flip injectors over and crank it see that all atomise the fuel no spraying as such, have seen a fair few valve springs loose pressure and cause misfire same as many head gasket related misfires as well, as its so low miles that car has been sat around more than running petrol goes off leaves a residue this could be the issue with dirty injector
 

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I recently bought an 05 plate Cooper S for my wife as our second car. It’s done 53500 genuine miles and is bodily in perfect condition ~ seriously like brand new! I knew it would need a new clutch and to rectify a steering cylinder leak, all of which has been done and she is running very smoothly...95% of the time! Every so often the engine warning light comes on and the car loses power almost exactly like “limp home” feature that I’ve experienced in other cars.....not sure if a Cooper S 15 years old has that? In any event the remedy is to switch off and restart the engine and it reverts to full power, again running beautifully. Three garages have been unable to diagnose/rectify the problem and this despite spending significant money on things like replacement plugs and ignition coil. Yesterday in the queue for car valet I was ahead of a home repair/servicing franchise van and he kindly linked me to his diagnostics iPad and it registered a misfire on cylinder 4 despite having the coil replaced last weekend. Suggesting just a loose connection and he having checked and tightened all of the them, I was anticipating no more trouble. Not to be.....the light suddenly came on on a journey today and the car lost power. I switched off and restarted and all was smooth on the journey home although the engine symbol light stayed on without any loss of performance.
I'm truly stumped....not a mechanic by any stretch of the imagination and now truly frustrated that I can’t rectify what must be a minor problem on an otherwise superb example of this iconic car. Can anyone help please?
The intermittent Limp Mode is most likely caused by failure of the Harmonic Damper. The center hub pressed onto the crankshaft snout turns, but the rubber layers between the inner hub and the outer pulley surface has failed, such that the pulley does not turn the serpentine belt and thus the supercharger does not turn which is what sends it into Limp Mode. The crucial thing here is that the water pump (driven by PTO box at the non-drive-end of the supercharger) doesn't turn either. You CAN drive it slowly in Limp Mode, but DO NOT drive it like that, pull over immediately or fatal engine overheating occurs quickly.

Replace the harmonic damper with a SuperDamper brand, and never have a problem with it again.
 

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The intermittent Limp Mode is most likely caused by failure of the Harmonic Damper. The center hub pressed onto the crankshaft snout turns, but the rubber layers between the inner hub and the outer pulley surface has failed, such that the pulley does not turn the serpentine belt and thus the supercharger does not turn which is what sends it into Limp Mode. The crucial thing here is that the water pump (driven by PTO box at the non-drive-end of the supercharger) doesn't turn either. You CAN drive it slowly in Limp Mode, but DO NOT drive it like that, pull over immediately or fatal engine overheating occurs quickly.

Replace the harmonic damper with a SuperDamper brand, and never have a problem with it again.
Oh and i bet the CEL code is either P1688 or P1689, neither of which is specifically "failed harmonic damper", but both have to do with failure to correctly calculate mass air flow/

 

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Many thanks to both Mikes for their advice above. The problem I have is that I am not a mechanic and so for any of these remedies I still have to incur significant labour costs at a garage, and having spent a good deal of money doing clutch etc. I’m struggling to find more and am under pressure from my good lady who loves the car but keeps saying we’ve bought a pig in a poke! I know we haven’t and am confident the car is a very sound investment with just this niggling issue to solve. What I need is a mini enthusiast fairy godfather who lives relatively close (Wokingham area) who would enjoy solving my problem for a couple of crates of beer plus parts! Cheeky I know, but I’m desperate to get it sorted somehow!! Nigel
 

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Many thanks to both Mikes for their advice above. The problem I have is that I am not a mechanic and so for any of these remedies I still have to incur significant labour costs at a garage, and having spent a good deal of money doing clutch etc. I’m struggling to find more and am under pressure from my good lady who loves the car but keeps saying we’ve bought a pig in a poke! I know we haven’t and am confident the car is a very sound investment with just this niggling issue to solve. What I need is a mini enthusiast fairy godfather who lives relatively close (Wokingham area) who would enjoy solving my problem for a couple of crates of beer plus parts! Cheeky I know, but I’m desperate to get it sorted somehow!! Nigel
if were the bottom pulley spinning then it would have more than a misfire on number 4 cylinder , it would have boost related codes and plausibility fault codes for boost circuit , also would over heat and the noise tends to give it away and belt chatter,
pull the ht lead off number on coail pack look at connection for same strange reason the factory coil packs corrode this one connector for number 4 worth checking
i misfire on 1 cylinder is due to 1 cylinder anything to do with ss drive tends to cause other issue and misfires on all cylinders even black rich petrol smelling exhaust gases as well and will flap up 02 sensor faults
 
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