R55 R55 Clubman Cylinder 1 misfire rough idle & overheating
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R55 Clubman Cylinder 1 misfire rough idle & overheating
Here’s a headscratcher for you guys. I bought a 2009 Mini Cooper Clubman Base R55 6MT with a N/A N12 motor back in August. Car had one of its tensioners seize up and chew up the serpentine belt, destroyed the two tensioners and pushed the belt on the inside of the crankshaft pulley damaging it and the front main seal. Replaced the tensioners, replaced the water pump with the updated metal one, new crank pulley, new main seal. Car ran great for 2-3 weeks until after a long drive it started to misfire with a rough idle and overheat. Misfire on cylinders 1&2, found out the radiator was also clogged up so changed it and no difference. Decided at that point that at 116k miles it’s about time for an overhaul. Pulled the motor out and changed everything on this list: New Oil pan gasket
New Oil pump chain
New timing chain
New timing chain sprocket
New timing chain hub bolt
New timing chain guides
New timing chain chain guide bolts, crush gaskets and seals
Both VANOS solenoids brand new (BMW N12 Motor in this car has dual VANOS, INLET & EXHAUST)
New Inlet and Exhaust VANOS camshaft gears
Both belt tensioners new
Updated metal water pump
New serpentine belt
New crankshaft pulley
New front main seal
New exhaust manifold gasket
New radiator
New Valve Cover Gasket
New NGK iridium spark plugs
New Multi-Layered steel head gasket +.3mm oversized to 1.2mm
New Head Bolts
New VANOS Camshaft Gear bolts
New intake manifold Gaskets
New Valve Cover PCV membrane
New PCV valve cover to intake manifold hose
New Transmission Axle Seals
Transmission oil changed with OEM transmission fluid
New Rear right Wheel Hub Bearing assembly
New Thermostat
New interstate battery
New throttle body to intake manifold gasket
New injector for cylinder 1
New injector seals
Cylinder head Resurfaced
New manual transmission output shaft seal
Cleaned out the pistons from an insane amount of carbon buildup as well. Put the car back together and it runs great… until it warms up after 10-20min of driving it or of it sitting running at idle. It starts to have a rough idle and misfires only at cylinder 1, temperatures have gone up as high as 226-230. Went over everything 2-3 times over and still can’t figure it out. Some mechanic friends are telling me maybe there’s an area of the motor where there is no coolant circulating building a hot spot but idk cause all this is isolated to just one cylinder. Plugs repeatedly get fouled in cylinder one and the smell out the exhaust of unburnt fuel is nasty. Switched coils over and the problem doesn’t change cylinders. Car was on on long enough where I got a stuck lean code from the pre cat 02 sensor, I guess a lot of fuel was getting sucked into the exhaust and triggered it, changed injector 1 to see if the rich condition in cylinder 1 would go away thinking it maybe had been stuck open or leaking and no difference. Help? About had my last straw with this car and am about a second away from trading it in for a damn Honda.
Update: I disconnected the ECT sensor from the thermostat assembly and drove the car for 30-45min no problem but with the radiator fan on the entire time. When I went to get gas, I shut off the car, started it up and even with the ECT sensor off and the the fan on it immediately started to idle rough and smell bad, threw a check engine light. After driving away the rough idle would be intermittent.
New Oil pump chain
New timing chain
New timing chain sprocket
New timing chain hub bolt
New timing chain guides
New timing chain chain guide bolts, crush gaskets and seals
Both VANOS solenoids brand new (BMW N12 Motor in this car has dual VANOS, INLET & EXHAUST)
New Inlet and Exhaust VANOS camshaft gears
Both belt tensioners new
Updated metal water pump
New serpentine belt
New crankshaft pulley
New front main seal
New exhaust manifold gasket
New radiator
New Valve Cover Gasket
New NGK iridium spark plugs
New Multi-Layered steel head gasket +.3mm oversized to 1.2mm
New Head Bolts
New VANOS Camshaft Gear bolts
New intake manifold Gaskets
New Valve Cover PCV membrane
New PCV valve cover to intake manifold hose
New Transmission Axle Seals
Transmission oil changed with OEM transmission fluid
New Rear right Wheel Hub Bearing assembly
New Thermostat
New interstate battery
New throttle body to intake manifold gasket
New injector for cylinder 1
New injector seals
Cylinder head Resurfaced
New manual transmission output shaft seal
Cleaned out the pistons from an insane amount of carbon buildup as well. Put the car back together and it runs great… until it warms up after 10-20min of driving it or of it sitting running at idle. It starts to have a rough idle and misfires only at cylinder 1, temperatures have gone up as high as 226-230. Went over everything 2-3 times over and still can’t figure it out. Some mechanic friends are telling me maybe there’s an area of the motor where there is no coolant circulating building a hot spot but idk cause all this is isolated to just one cylinder. Plugs repeatedly get fouled in cylinder one and the smell out the exhaust of unburnt fuel is nasty. Switched coils over and the problem doesn’t change cylinders. Car was on on long enough where I got a stuck lean code from the pre cat 02 sensor, I guess a lot of fuel was getting sucked into the exhaust and triggered it, changed injector 1 to see if the rich condition in cylinder 1 would go away thinking it maybe had been stuck open or leaking and no difference. Help? About had my last straw with this car and am about a second away from trading it in for a damn Honda.
Update: I disconnected the ECT sensor from the thermostat assembly and drove the car for 30-45min no problem but with the radiator fan on the entire time. When I went to get gas, I shut off the car, started it up and even with the ECT sensor off and the the fan on it immediately started to idle rough and smell bad, threw a check engine light. After driving away the rough idle would be intermittent.
Last edited by Clubman4361; Nov 19, 2020 at 06:52 PM. Reason: Added engine type
Sounds very, very similar to our R56.
Same symptoms : Drive it for a while and it starts to misfire on one cylinder. I think ours was #2.
Scope revealed that it had dropped a valve seat, which seemed like the obvious solution.
Thousands of dollars later for fixing the head, still had the same symptoms.
Replaced the PCV, valve cover, etc... still didn't fix it.
We cut our losses and ended up giving it to a B-Spec racer who got it running right, but then it kept dropping valve seats, so he put a totally new head on it and he's back to racing.
Not sure if that's helpful to you, as whoever resurfaced the head probably would have noticed the valve seats being messed up, but who knows.
Good luck!
Same symptoms : Drive it for a while and it starts to misfire on one cylinder. I think ours was #2.
Scope revealed that it had dropped a valve seat, which seemed like the obvious solution.
Thousands of dollars later for fixing the head, still had the same symptoms.
Replaced the PCV, valve cover, etc... still didn't fix it.
We cut our losses and ended up giving it to a B-Spec racer who got it running right, but then it kept dropping valve seats, so he put a totally new head on it and he's back to racing.
Not sure if that's helpful to you, as whoever resurfaced the head probably would have noticed the valve seats being messed up, but who knows.
Good luck!
Thread Starter
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Neutral
Joined: Nov 2020
Posts: 4
Likes: 0
Sounds very, very similar to our R56.
Same symptoms : Drive it for a while and it starts to misfire on one cylinder. I think ours was #2.
Scope revealed that it had dropped a valve seat, which seemed like the obvious solution.
Thousands of dollars later for fixing the head, still had the same symptoms.
Replaced the PCV, valve cover, etc... still didn't fix it.
We cut our losses and ended up giving it to a B-Spec racer who got it running right, but then it kept dropping valve seats, so he put a totally new head on it and he's back to racing.
Not sure if that's helpful to you, as whoever resurfaced the head probably would have noticed the valve seats being messed up, but who knows.
Good luck!
Same symptoms : Drive it for a while and it starts to misfire on one cylinder. I think ours was #2.
Scope revealed that it had dropped a valve seat, which seemed like the obvious solution.
Thousands of dollars later for fixing the head, still had the same symptoms.
Replaced the PCV, valve cover, etc... still didn't fix it.
We cut our losses and ended up giving it to a B-Spec racer who got it running right, but then it kept dropping valve seats, so he put a totally new head on it and he's back to racing.
Not sure if that's helpful to you, as whoever resurfaced the head probably would have noticed the valve seats being messed up, but who knows.
Good luck!
Thread Starter
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Neutral
Joined: Nov 2020
Posts: 4
Likes: 0
hmmmm, that actually does sound like it could be that, will bring out the multimeter and see whats up with the loom
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