Intermittent misfire

[fluffy01016]

strange one for you, my fault code reader told me that I had an intermittent misfire on cylinder 3 so I swapped the plugs from cylinder 3 & 4 and the fault stayed on cylinder 3. My assumption was the coil pack so I got a second hand one from eBay and all was well. I decided to change the plugs anyway and fitted them about 4 days ago. Now I've got an intermittent misfire on cylinder 2 & 3 and a separate warning for intermittent misfires. The car this morning stalled and under load had black smoke coming out the exhaust. Not sure what it can be?? I didn't gap the plugs before I put them in, could this be the misfire?? I'm not losing water and oil looks clean so hopefully not the head gasket. Only other thing I can think of is the injectors but would be surprised if 2 failed at the same time

Thanks as always for any help offered

[fluffy01016]

Sorry should have added that it's a 1.4 mpi

[hutchysrs50]

What engine is it?

1.4 16v - possible worn valves.

A compression check would be good as a base point.

[fluffy01016]

It's the 8v version