Hello ,

Symptom: Rough unsteady idle upon cold-start, Engine became smooth after 4min running. This has been going on for 1 week then car finally through a CEL (p0303), cylinder-3 misfire. I'm like d@mn, spark plugs and ignition coils were replaced 10K miles ago. Anywhoo, I start basic troubleshooting, swapped ignition-coils between cylinder-3 & cylinder-4, cleared CEL and drove car to see what happens. Same cold-start rough idle and low and behold, CEL (p0303) pops up again. So, this rules out a bad ignition-coil. I precede to order new spark-plugs from rockauto, Removed spark plug for cylinder-3 and it looks like:



Anyone ever see a spark plug with 40% of porcelain around electrode missing? Jeezz only on Mini :-)

I've not driven car yet after spark plug replacement. Once I do, I'll post back here and let you all know the status

 

Yep seen them crack and fail on the N14 engines. I think its that beru design plug or pre detonation /excessive heat that happens.

 

Which plug manufacturer and model?
(looks like NGK)

 

Might have been dropped.

 

Spark plus make/model is: NGK ILZKBR7B-8DG (NGK 97968).

Also, finally started and drove car (8-miles). Cold-start engine performance is back to its normal smooth self with no new CEL so, I call it 'a win'.