1.Rough running, which yours is,
2.Loosing water, check the coolant level,
3.Pressurising the cooling system, so after a short run if you remove the rad cap it would throw most of its coolant out (please dont burn yourself, I wont be held responsible!!!)
4. Overheating,
5. Yellowy/grey sludge under the oil cap and in the rocker cover.
Most garages can perform a 'sniff' test to determine if the head gasket has blown too.
And changing the head gasket aint hard IF your a competent home mechanic, but get it diagnosed first, it'll be a lot cheaper.
it is very possible that a spark plug or a spark plug wire has gone bad rendering that cylinder bad because no spark!
need to know the make and model of the car. could be injector, plug, wire, coil...... hard to diagnose if I don't know what im working on
Perhaps it only has 3.
Probably a valve.
cuz the forth one is ****** up i guess
