2004 1.6 Focus misfire

[Avocet]

I've got a mate who is struggling with an 04 Zetec Focus 1.6. Persistent misfire on No. 4.

Coil pack, plug and plug lead changed, but no better.

Any thoughts please?

 

[Spark123]

Have you tried an inline spark plug tester? Just to make sure the misfire is being caused by the sparkplug not firing.
Have seen a misfire caused by an air leak on the inlet manifold, just by the butterfly valves when the end cap fell off.

 

[Belle427]

and then a compression test, maybe a valve isnt seating properly.

 

[Burnerman]

A fuel injector in the huff?
Look for around 16 ohms across the terminals.
I would have thought the management light would be on though - unless it is a compression issue.
John

 

[Avocet]

Thanks all. I'll pass those on.