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Cooper S rough idle :(

8K views 4 replies 5 participants last post by  nsm3 
#1 ·
Since buying my Cooper S at 49k the idle has been fairly rattly, almost like a diesel except I drove an Cooper SD and it was smoother!
ever since I've had it I've always used V power shell petrol and I've flushed the engine with redex and gave it a new oil filter an proper oil!
I thought maybe it was the lower engine mount so I bought a poly bush one (if it was due to a bad engine mount then I would've been okay to cope with vibrations through the poly bush) but the engine mount was perfect. replaced anyway and literally NO difference at all to the idle feel in cabin.
It definitely gets worse when the AC is on, feels like a town bus!
The only thing I can think it could be is spark plugs, I've heard bmw sometimes mixes them up between champion an NGK which can cause a few issues (is this even true?)
if not, what else shall I look out for? car does seem to use a lot of fuel, 20mpg mostly! though I do push it a fair amount. :)
 
#3 ·
I used to work as a petrol station assistant and sold all the main U.K. fuels except Esso. Using the top Shell fuel, you really shouldn't need to use Redex as the fuel already contains a similar additive of 'stuff' to keep everything clean. I was very much 'in tune' with one of my previous cars and always knew whenever my husband had put Shell fuel in it (even though I worked in a BP station at the time). The car was always that bit better on Shell although BP was my second favourite fuel.
Sorry I cannot help with your actual question but hope I can at least save you a little money that you're spending on Redex.


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#5 ·
I've just put our F54 S on charge and had the engine running with the bonnet up. I noticed how rattly it is also. Back in my old Mk3 Cortina days, that noise would herald a camshaft replacement!

It disappeared with some revs, but sounds rough 'as' on idle. Only 3.5k miles on this one.
 
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