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Misfires when hot

3516 Views 3 Replies 2 Participants Last post by  mike1967
For weeks I have been following advice I find by googling on how to address a problem I am having with my 2008 mini cooper base model where it runs great until the engine gets warm, then, it runs like hell, most notably when I am stopped and idling - like after coming off the highway to a stop light. Engine will come on sometimes when this happens, and then often will go out the next time I drive it. Getting a misfire code from piston 2. Here is a list of things I have had done... 1. all new plugs. 2. cleaned and put back the VANOS and cam sensors. 3. swapped plugs and coil into cylinder 3 (misfire code remained in cylinder 2). 4. had compression check done (all good - only 5% leakage in cylinder 2 actually). 5. BMW ran what they call a DME scan for operational smoothness which showed that results were too high in cylinder 2 (I have no idea what that means). They also said plug 2 was quite wet and maybe this is what is causing the misfire - its getting too much fuel? The next thing they want to do is swap the injectors - and they want to charge me $468 dollars for this. If the problem does not follow the swapped injector, they say its new engine time. I guess the question i have is this... what is the likely hood of an injector that works when cold, but not warm? Also, i can't seem to find any video on replacing injectors for the R56 base model. Thanks in advance!
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before throwing money at new injectors i would remove the fuel rail with all 4 injectors on it and crank engine over and watch how they give out the fuel,, ie a perfect one should atomise the fuel ie cloud of vapour, so all 4 should look the same, if one dont ie number 2 then you know its that,, but if the car has been driven around for long time chances are might of caused piston ring wash from unburnt fuel in that bore, put id compression are ok then should be ok. those engines have a habit of cracking valves this crack opens up with heat and will cause a misfire to come and go i have seen a lot of them go like this, new engine need not be the answer, ie head off replace the valve and head gasket and head bolts and while in there a new timing chain kit as well as chains need changing around the 60.000 miles mark. also if you were to change engine finding a genuine low mileage engine for that would be a battle and probe over £1500 plus £500- to £1000 to fit it, and that would be on a timing chain already used as such, on those engine because they are expensive to buy is worth the repair then you know you have a good one,
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before throwing money at new injectors i would remove the fuel rail with all 4 injectors on it and crank engine over and watch how they give out the fuel,, ie a perfect one should atomise the fuel ie cloud of vapour, so all 4 should look the same, if one dont ie number 2 then you know its that,, but if the car has been driven around for long time chances are might of caused piston ring wash from unburnt fuel in that bore, put id compression are ok then should be ok. those engines have a habit of cracking valves this crack opens up with heat and will cause a misfire to come and go i have seen a lot of them go like this, new engine need not be the answer, ie head off replace the valve and head gasket and head bolts and while in there a new timing chain kit as well as chains need changing around the 60.000 miles mark. also if you were to change engine finding a genuine low mileage engine for that would be a battle and probe over £1500 plus £500- to £1000 to fit it, and that would be on a timing chain already used as such, on those engine because they are expensive to buy is worth the repair then you know you have a good one,
Thanks Mike. I read a post about exhaust valves causing an issue like this. I suppose that could make sense why it happens when hot and not when cool.
cant know for sure until go through all the other processes, i've seen sticking valve do same trick, start off with compression tests when engine is hot might show i up
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