Random and cylinder 4 misfire ?!!

[Mik]

Hi, any ideas for the following -
Had a random misfire and cylinder 4 misfire reading. Changed coil and spark plugs but still get the reading.
Has anybody got any ideas where to look next?
Many thanks......

 

[nluk100]

Blocked injector? Try swapping one over with another cylinder. Did you check the thread on cylinder 4 for damage (cross-threaded/stripped)?