Chiti Chiti... Bang! Bang!

A friend came round and had a look at the Jag and noticed an arching sound from somewhere near 6B or 5B. Everytime it arcs, the engine shakes and backfires slightly.





(Left to Right: 1B to 6B) As you can see all the plugs are covered in dark soot. According to the Haynes manual this is either Preignition or Detonation. In both cases electrode gap and/or timing are causes.


The Haynes manual also says these sooty oil deposits are caused by oil leaking into the combustion chamber due to worn valve guides or piston rings. That might explain the backfire, hesitation and white smoke from the left exhaust, but God I hope not.

(Left: 1A, Right: 1B) I knew Bank A was running perfectly so I decided to pull the plug in 1A and compare it to 1B. There is obviously something going on. But my lack of expertise halts any further diagnosis.