Cold start missed fire on EZ36

[oakleyyu]

Hi everyone! Just wonder how would I be able to deal with a cold stater missed fire on EZ36 travelled around 100k?
Have changed to new plugs already no clear signed of leak from head or failure in gasket, a little missing fire in one cylinder (closest to passenger side, cylinder6 I think) when cold start but return normal after running hot. Check the compression ratio and unsurprisingly its lower than standard (8.25bar for the missed fire cylinder and 9bars around others, 10.5bar is the standard sepc) Is this a typical subaru thing or I should do something now, cheers!

FYI, I've got a 2015 Subaru Liberty 3.6R, the car has been serviced regularly with quality fuel and suitable grade, I've also suspect it might be a ignition coil problem so I swap two coil when changing the plug but the problem stayed with the cylinder. The over all condition of the ignition coil does not look bad though.

The problem is not even noticed a problem as I thought the rattling and noise is normal for this car when cold start, and never had I got a light in dash, until I bring it to mechanic, plug in a obd, it can have numbers showing missed fire in cylinder 6.

[bigBADbenny]

Scope for misfires is broad, try your FSM for the diagnostic procedures.

Do you still have the old plugs eg make photos of the tips for reading them.

Basically you want to do all the easy least intrusive tests re looms & loom plugs before eg pulling the cam cover and checking valve clearances.