broken timing belt
Check the valve timing and the ignition timing. If both are good then check the compression in all the cylinders.
bad rings most likely burnt valves i would also suspect a blown head gasket between those 2 cylinders
It may need spark plugs/wires. And while you're at it, run a compression test. If the compression is low in one or more cylinders it will make those cylinders less likely to operate properly.
Not running on all cylinders? Check spark plugs and wires Do a compression test to see if one cylinder is dead
I'm not sure of the exact values; they should be in your Haynes repair manual. However, if you compression test all of the cylinders and find one that is lower you have a compression problem with that cylinder. It is also possible to have 2 that are lower, this would most likely indicate a warp in the head between those two cylinders. Other causes for compression loss are damaged or gunked up valves that do not close all the way or a crack in the head.
Not running on all cylinders? Bad plugs, wires, or valve? Try a compression test to see if problem is internal to the engine
sounds like bad head or gasket do compression test on cylinders
Check condition of the plugs, could also be coil pack(s) going out, if ignition looks good check compression all cylinders
It is very possible that you might have a blown head gasket. However, other causes of low/no compression could be a cracked head, a cracked piston, or burnt valves. ANOTHER ANSWER It depends on the way the compression is down. If it's low on two adjacent cylinders, it's probably a head gasket. If it's just one or more non-adjacent cylinders it could also be burned exhaust valves. If it's low on all cylinders it's probably a slipped timing chain/belt.
You think probable to compression.
b:normal fault
Check your spark pugs...it could be that or worse case it could be a compression problem with one of your cylinders