I own a r56 hardtop, cooper s with about 96k's on it and ive been having a few problems. the first and biggest problem is that my car sometimes just loses rpm's or just wont go like it just lost all torque and backfired a LOT. sometimes when i try to take off from a standstill in first it just konks out and wont pull than ill have to push the clutch back in and give it about 3,000 revs than change in to 2nd and it goes away. or other times i will be on the free way and it stars loosing revs and again with the backfiring and ill have to start downshifting and giving it gas and it would not even do anything, i could have my foot hard on the loor and nothing would happen, and eventually it goes away after a bit. The mini also feels like it loses compression or maybe something with the spark plugs which i suspect have never been changed.
I think that it may be the spark plugs, once i put in 93 BP fuel and the car got absolutely convoluted and make horrible noises and backfiring and gave about 17 mpg and i was driving normally. after putting spinx(local gas station) fuel in it it went back to normal by normal i mean the previous paragraph.
Ever since the BP indecent ive been getting much lower fuel ecodemy about 26 mpg compared to the 30+ mpg i had before. can somebody please tell me whats wrong with my car
Much thanks, Josh from Grenville, SC
P.S the car hasnt had a service in about 40K's i just haven't had the time or the money and i got the car at 50K's with one owner for the most part brand new.

 

By no service to the car in the last 40k miles you are still doing oil changes at the bare minimum right?

Some things I'd look at if I were you and they are cheap is air filter (make sure it is clean).

Check spark plugs (make sure they are ok, I just cleaned mine as I didn't want to spend the money yet, its only 40 bucks on ebay but still it adds up).

I also heard these minis have a fuel filter, its located under the rear seat and it doesn't look to easy to change but that might have something to with it as well.

Most likely its your catalitic converter as it sounds like issues other's are having. However I'd check the above before I even moved forward.

 

Yes i have been doing my oil changed about evrey 5K and i do have to get a new air filter and spark plugs. not sure about the fuel filter though i have to loom at that, thanks for the help.

 

check for codes. Your local parts store will usually run a scan for free.
Intermittant issues are usually electrical.

 

Are you having issues when starting the car and the engine is cold? If so then I would suspect the high pressure fuel pump. It's a common fault. You can monitor the pump pressure with a OBD2 scanner and a smart phone app.

That being said, it's nearly impossible to properly diagnosis a modern car via the internet. You'll end up having 100 different people tell you 100 different things. (myself included) So, have you though about taking the car to an independent shop and have them run some diagnostics? It will probably be the cheapest route in the long run.

 

it not cold here in south carolina yet sono not really ive taken the car to auto zone 3 times and only once they said the engine was misfiring and the sparkplugs where bad so i dont know. i also took my mini on a road trip last week to atlanta and before i left the coolant was full(with water cuase im lazy) and by the time i got back mare than half of it was empty. do you think that has something to do with it? P.S nice cooper

 

It would be worth while to look at the plugs. It does require a 14mm 12 point thin wall socket. And stay away from the generic brands of plugs. I'd stick with then Beru OEM plugs. A falling high pressure fuel pump will give misfires but so will bad coils and plugs and carbon buildup on the valves. If the misfires are only on one cylinder then swapping the coils around will help in diagnosing, for example if the misfire follows the location of the coil then that's a likely culprit.

Fours things to look at:

1, High pressure fuel pump (very common failure and I meant a cold engine as in the first time you start it for the day).
2. Plugs
3. Coils
4. Carbon build up on the valves (very common for the N14 motors - which you have - and only walnut blasting will solve the problem. This should cost no more than $400)

As far as losing coolant, the thermostat housing are notorious for cracking and leaking. Sometimes they only leak when driving so you may not see a puddle while parked. Keep an eye on that.

 

thanks m8 ill check on it and see if thats the problom. thanks for the help.