Posted by lee mackintosh on April 13, 2008, 2:17 pm, in reply to "Re: Update"
if the compression is low due to worn piston rings then this may be the reason fro the loss of cylinder as the spark plug is being fowled up at idle but at higher engine speeds it can burn off the oil ok.
Its amazing how much a loss in compression can cause engine running faults as i've found out at a cost with a rover after a head gasket change that didn't go according to plan.
An extra 30psi in compression was the result in good running with my rover problem, may be new rings on your fiesta will be a good result.