Misfire at 54,000 miles

16 October 2014 - Filed under: Repairs

The MINI developed a shake and loss of power under load. At first I was worried that the clutch was slipping, but then the check engine light briefly illuminated. This did at least give me a good excuse to use the WiFi ODBII adapter I’d previously purchased and never really done anything with. The fault code revealed a misfire on cylinder 4.


Coils or spark plugs seemed the most likely cause, however despite the car constantly shaking under load I couldn’t get the warning light to illuminate again, so moving the coils around to see if the misfire moved cylinders didn’t reveal much.

Euro Car Parts had the best price on the same Beru plugs that the MINI left the factory fitted with – £26 for a set of four. You need a slightly unusual 14mm 12point socket to fit and remove them.

I foolishly got tempted by a secondhand set of coils from Mintech spares. I didn’t want to throw too much money at the coils until I’d confirmed that they were at fault, so a secondhand set of four removed from a 2010 MINI for less than the cost of a single new coil seemed like a good idea at the time.


New parts


Fitting was simple enough, for some reason the Cooper and Cooper S differ in that the coils are covered by a bit of plastic held down by two T30 Torx screws. With that removed the connectors can be unplugged from the coils, they then pull upwards and out revealing the spark plugs. The spark plugs need to be torqued to 20NM. The original plugs didn’t look too bad, so I think the coil was at fault, a new set of plugs won’t hurt though. I might ask the MINI dealership to give me the new set of plugs the car is due to have when it goes for the final TLC XL service in 6 months.

With new plugs and the secondhand coils in place everything ran perfectly… Briefly. After a few miles one of the secondhand coils packed up resulting in a constant misfire on cylinder 3. I swapped it over with one of the working original coils and everything seems to be happy again. Lesson learned, don’t buy secondhand service parts. That said, they were cheap and allowed me to confirm that it was definitely the coils causing the issue. I’ll go ahead and order four brand new coils now that I know.

For reference the factory fitted coils are Bosch 0221504470, the spark plugs are Beru 12ZR6SP03. The Cooper S uses NGK plugs rather than Beru.

Comments x 3

  1. David WilliamsEurope 22 October 2014 - 9:21 am

    Many thanks for keeping this blog running through your tenure; its been invaluable reading as a prospective R56 owner, and the TIS links are the icing on the cake.

  2. whistlerEurope 24 October 2014 - 7:42 am

    Nice blog with many informations, many thanks from germany! .-)

  3. MattUnited States 10 May 2018 - 9:06 am

    Came across your blog, I’m not very mechanical but I bought plugs and coils and it looks like an easy job. The Beru site recommends a little dielectric grease on the plugs, but I’ve seen people say not to use any grease… Did you use grease with your plugs?

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