S40 2.0T starting problems and misfires

[Conrad]

Hi everybody, first post, please be gentle!

As the title says, my S40T, 113000 miles is having some problems starting - it takes over ten seconds of turning over to finally start. Also, it very occasionally misfires when decelerating on a motorway. Other than that, it runs beautifully.

Haven't had it all that long, but I have changed the battery and the MAF, and previously the alternator, lambda sensor, plugs and leads, and fuel filter were changed quite recently I believe.

One weird thing - twice before I've left it for three weeks without starting it at all, and after three weeks, on cold wet mornings, it's started first time!
I've searched the forum and it sounds like I need to get the compression checked, but as it runs OK, and can start first time I was wondering if anyone had any other ideas?

Thanks for your help!

[niloc]

Check:

Timing
Compression
Cam position sensor