If you suddenly find yourself experiencing a misfire in your MINI Cooper S, a burnt out valve could be the cause. Although not a common failing, numbers of these cases are on the rise. A poor combustion mix can raise cylinder temperatures and increase the chances of this occurrence.

Inlet valves becoming contaminated with carbon deposits can be one cause of this. An engine decoke is a great thing to carry out on any N14 especially of higher miles. An increase in BHP is also a nice benefit of decoking your inlet valves

Thorough maintenance including regular oil changes can reduce the carbon build up.

Another cause of increased cylinder temperature is a faulty fuel supply system. The high pressure fuel pump is a well documented weak spot. A failing injector could also add to the issues.



The cause of the misfire and the effect of the poor fuel mixture. Notice the deposits on the valves heads!



Heavily contaminated inlet valves. The carbon build up, a nasty effect of direct fuel injection. The inlet valves were removed and this build up cleaned off.


A fresh new valve against the burnt original.