Focus 1.8Tdci Mis-Fire

[Timty]

Hi,

I have a 2009 (last of previous model) 1.8 TDCI Focus. I bought it new and it has 40,000 miles covered.

Driving, usually at a constant speed on the motorway, it can give an instantaneous and quite violent misfire that lasts for a split second. It's as if the engine switched off for 1 millisecond and back on again. Having happened, it might not happen again for the next 60 miles or so. On short journeys about town I never notice it, only always on a motorway journey but not always.

No other symptoms, no lights or codes and no loss of performance.

I have changed the fuel filter a number of times (3 times over the last 12,000 miles) hoping to cure the issue but no good. This is an expensive practice as Fords charge 48 euro for a filter element, i fit it myself.

Have any of you experienced this issue, it's hardly normal behaviour.. is it ?

Thanks