I've a problem with misfiring in # 5 cylinder -combustion failure

USA spec car no not? no country of VIN told so answers can be big time wrong, ok?
sure get a shop to fix it
they have tools you don;'t have.
3.0L is inline 6? called L6
is this car with coil pack that does more than one spark wire?
or have 6, COP spark coils, (all I can do is guess)
or USA has 6 COPS
we check compression first, x6.
got cam timing chain NOISE?
I guess changed word mean replaced, with new COP coil?
well; engine is first , the spark then fuel injector
do DTC P0301 was set, and is still set this error, be specific on DTC errors, even tell them.
301 means weak combustion on #1

• bad cylinder compression
• bad spark
• or #1 injector is bad.

why 3 and 5 fails and all are odd cylinders./
is odd but I suspect VVT problems./
no mileage on the engine told. 300k 400k?

It sounds like you have a leaking engine cylinder head gasket, the combustion gas causes the coolant tank to pressurize and that is what you see.

Probably a coil or the connector that goes from the coil to the spark plug.. unplug one coil wire at a time and listen for RPM loss.. The cylinder with the least RPM drop off could be your problem. Change that coil to another cylinder .. see if the problem travels with it.. if it does you have found the problem..Remove the coils and check the connectors for cracks and carbon tracking.. if it does not travel check the spark plug. This is a large problem.. missing cylinders leads to bad cats.. a very very expensive problem.
Look to rockauto.com for parts.

Sounds like water is going in to your engine. Check the dip stick out to see if it's milky.

check the injectors with a noid light you may find a bad one. if not check the compression.

yes... overheating can cause issues in your piston/cylinder head. if your cylinder head is made from aluminum and not metal, overheating can cause cracks and bends in your cylinder head. if this cracks occur inside the combustion chamber, then proper compression cannot be attained. you need to rebore then resleeve your combustion chamber and change the pistons to fix this issue. this will also require resurfacing of cylinder head to ensure that it does not create leaks against crankcase.

could be a vacum leak the break system uses an air diaphram to help assist on the power side of the breaking system go to how stuff works .com and look up how breaks and mastercylinders work it will explain how it uses vacume to assist the master cylinder but it sounds like u have an vacume leak

YOU HAVE PROBLEMS WITH SUCTION HOSE ON TOP TO MOTOR THAT CAUSE MISFIRING ON ALL CILINDERS AND TRY REPLACE CRANKVENT VALVE THAT HELP STOP SMOK

the best way to diagnose a misfire is to move the ignition coils of those cylinders(4 and 5) to different cylinders to see if the misfire will move. you can also move the injectors around and even the spark plugs.(make sure to keep a good record of where you are moving them). if you can't get the misfires to change cylinders. your next step would be to do a compression check on all cylinders. air leaks in the intake system can cause misfires but usually it isn't on the same cylinders all the time

This is a pretty common problem. I would change your valve cover gaskets. They run around ~ 50 bucks. If they are bad it will leak oil into spark plug well and cause a misfire. Very known on the 740.. Also if tune was not anytime not too long ago id change spark plugs while you at it. Then clear the computer and if you still get misfire on 8 try changing the ignition coil which is right about the cylinder with cylinder ignition coil 5. clear the computer. if you get random misfire and misfire cyclinder 5 after then its your ignition coil. parts store runs around 100 bucks