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Discussion Starter · #1 ·
Hello,

Recently my 07 mini one (50k miles) will completely stall when idling after the engine is warm (usually after about 20 min run on the motorway). I have not noticed any change in power or strange noises but as soon as I lift off the accelerator and the revs fall below 1k it quickly sinks below idle level (800ish) and cuts out (stop start is turned off) I have to turn the car off and on to get going again. The car had reported a pre-cat o2 sensor failure which I have replaced which cleared the error and engine light but the problem still persists. I no longer receive an engine light but I am getting a 2B68 code (air-mass flow plausibility). I have read it could be the crankcase breather pipe, should I attempt to replace this or is there something else I should be checking first?

Thanks in advance!
 

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make sure oil filler cap has its rubber seal, also the dipstick is all way in , after that could be pcv valve in rocker cover or the plastic pipe at rear of rocker cover is very common as its a 2007 car it will have the earlier type if never replaced before and cars age would sit with the plastic cracking,, what happens is it allows unmetered air in to inlet manifold the mass air flow sensor sees this as a plausibility ie running out of spec, the extra air or 02 that is un metered in the system gets the 02 sensor upstream confused it tells the ecu to add fuel to try and balance the trim,, so could very well be a bi-product of the extra air form the pipe or and rocker pcv valve,
it could also be a timing chain issue where chain so far stretched the over lap on valves is adding to the effect. at 50.000 its well on its way for needing to be replaced anyway, as 2007 car chances are due to age the valve stem seals will be hard from heat and age as made of rubber this also can cause same issues as they coated the rear of exhaust valves and go hard and causes misfires this leaking dumps unburnt petrol and air on to pre cat 02 sensor it also will burn a hole in the cat if not found sooner enough,
 

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Discussion Starter · #3 ·
make sure oil filler cap has its rubber seal, also the dipstick is all way in , after that could be pcv valve in rocker cover or the plastic pipe at rear of rocker cover is very common as its a 2007 car it will have the earlier type if never replaced before and cars age would sit with the plastic cracking,, what happens is it allows unmetered air in to inlet manifold the mass air flow sensor sees this as a plausibility ie running out of spec, the extra air or 02 that is un metered in the system gets the 02 sensor upstream confused it tells the ecu to add fuel to try and balance the trim,, so could very well be a bi-product of the extra air form the pipe or and rocker pcv valve,
it could also be a timing chain issue where chain so far stretched the over lap on valves is adding to the effect. at 50.000 its well on its way for needing to be replaced anyway, as 2007 car chances are due to age the valve stem seals will be hard from heat and age as made of rubber this also can cause same issues as they coated the rear of exhaust valves and go hard and causes misfires this leaking dumps unburnt petrol and air on to pre cat 02 sensor it also will burn a hole in the cat if not found sooner enough,
Hi Mike,

As usual thanks for your excellent reply.

Would the entire rocker cover need to be replaced or can the valve / plastic pipe be replaced on its own?

Do you also know where I could find spare T40 torx screws for the engine cover, one of the screws is looking a bit stripped.
 

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Hi Mike,

As usual thanks for your excellent reply.

Would the entire rocker cover need to be replaced or can the valve / plastic pipe be replaced on its own?

Do you also know where I could find spare T40 torx screws for the engine cover, one of the screws is looking a bit stripped.
it is possible to replace the valve but the spring is the painful bit as very sensitive to spring strength to work correctly.. way to check the valve is to remover the inlet manifold and remove the plastic breather pipe and connect the pipe to rocker cover and if you blow or suck can remember which it will flow pone way and not the other if that makes sense,
below links i have used in past and seemed to do the job ok,
or this one for non turbo
should be held on with 10mm bolts if not someone has added torx
 

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one added point if the temp sensor is fault for coolant that would also cause a issue, another thing is timing chain around 60-90k will cause it, damaged cat will so will valve stem seals when dump oil on to the valve seats,,
all of the above is not just mini engines its a widespread thing i do as many vag petrol engines with same issues from timing chains and stem seals etc,, this is all bi-product of building cars as light as possible and then add emissions crap on top,, ie egr and cat and dpf all have a neg effect then add 20k services its just not very good for the owner great for the car maker
 

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Discussion Starter · #6 ·
Afternoon,

Hope your first lockdown V2.0 weekend is going ok!

I had a chance to have a nose under the bonnet: Oil cap seal is in place and the dip stick is 100% all the way in. I took a look at the PCV Valve and couldn't see any issues (Image below). The plastic pipe, (I assumed it is left of the PCV Valve?) seemed fine but was soaked in oil, not sure how much of a issue that is?

279069


I took a video of the engine sounds, couldn't feel any vibration on the timing chain or any sound coming from it directly (replacement of it is on the list, just need to save up a bit). I am also getting a fair amount of white smoke out the back.

Is there anything else I should take a look at?
 

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they do smoke a bit when cold until get exhaust totally hot then dont tend to, also if cold weather all cars do, if breather pipe is covered in oil then its cracked prob where cant see it its inlet manifold off, if cracked will cause idle issues, timing chain can sound perfect but still be stretched and engine out of time, also on newer cars or cars with latest spec tensioner they dont make any noise until fail no warning ,
prince engines are noisy compared to most engines due to vvt and direct injection on turbo cars.. mot emissions test will show if all is not well
 

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Discussion Starter · #8 · (Edited)
Apologies for not being clear, the smoking was after the car had been driven for about 30 mins.

I took a look at some of the data streams for the engine to see if anything looked off, the main thing was the smooth-running value: Cylinder 1 & 4 are both constantly below 1.00, Cylinder 2 hovers around 2 - 5 and Cylinder 3 is going pretty nuts, jumps erratically from 21-400 and everything in between. The intake-manifold pressure is 957 hPa at idle (when warm) vs 1009 ambient, I tried to research what the normal pressures should be but couldn't find any results.
279082
 

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cylinder 3 needs a leak down test, and compression test looking for perfect engine on turbo engines 190psi anything above 140psi will do, but all need to be even,
on non turbo 160psi to 140psi, would say number 3 cylinder is at fault,, remember number 1 is gearbox end on these engines.
 
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