Any help is appreciated. Was driving and without any strange noise or warning a steady misfire started. Vehicle is chain drive NOT belt. 90k miles Did code check P0304 "permanent" and won't clear. Changed all spark plugs & cyl#4 ignition coil. Battery was disconnected during repair. Reconnected battery. Code remained. Started CR-V still had a heavy miss on cylinders #4 & P0304 still remained. Swaped around coils. Miss still on cyl 4 with code. Pulled all spark plugs to do compression test. Results are
cyl#1 approximately 200psi
cyl#2 approximately 200psi
cyl#3 approximately 60psi
cyl#4 approximately 0-7psi
no coolant loss or overheating. No coolant in oil.
Pulled off valve cover to visually inspect valves, valve springs & cam. Disconnected injectors. And turned enging to see valves moving. Everything moves as it should. NOTHING VISUALLY BROKEN OR NOTABLE
Put cyl #4 at TDC. Applied shop Air to cyl 4 and can hear air escape into intake manifold & come out of cylinder 3 spark plug hole.
Car very well taken care of. Not driven hard ever.
Trying to help out a family friend. Single mom in a tight spot
Please help!!
???what do you guys think?????

Piston Rings?
Cracked Head?
broken valve seats?

 

welcome to the forum. glad you're trying to help, my thoughts, possible blown head gasket, when you take the head off, you can also check for valve leak or do a visual on gasket. if you replace head gasket, mill the head to eliminate possible warp, kind of unusual for 90k and low compression.