I just changed the spark plugs on the Zetec-S. The ford service guide lines for spark plugs are 40,000 miles between replacement.

The plugs i took out were well worn on the tips of them. The new plug were all gapped to 1.3mm (as per guide lines) and i measured the gaps on the ones that came out, they were rangeing between 1.6 - 1.7mm. Does that gap sound rather large to anyone considering the correct gaps are 1.3 mm ?

i guess as the gaps are wider the spark must be later, does the ECU of the Zetec-S detect this and make adjustments to the ignition timing to compensate for the wider plug gaps ?

p.s i wont be leaveing this set of plugs 40,000 miles again, they will be changed ever 10,000 service without fail no matter what Ford say

 

The ecu cannot detect plug gap size.
The coil is over rated in terms of voltage to compensate for a bigger gap.

The wear rate of the plugs depends on how hard you drive the car and the quality
of fuel used.

Also, as a comment. Coil pack equipped cars will always wear out plugs quicker
than a car with a dizzi as plugs are fired in pairs (Wasted spark method)

I.E. twice as often.
when one plug fires normally on the compression stroke,
the opposite plug is fired on the exhaust stroke.
Usually plugs 1 and 4 are fired together and 2 and 3 together.
This is for an engine with firing order 1342

 

Cheers simon i hadnt thought about the wasted spark having an effect on spark plug life.