:right: well it may be injector error it may be a slipped timing belt
and it may be faulty valve set....
could faulty fuel pump supply....
if you replaced spark plug and spark lead lead
and you replaced the dizzy and coil pack
you could have a blown head gasket ?
you could have bent or faulty valve ?
check the injectors and check that each is producing the same flow amount
measure it in a cup for each cyclinder
if this prooves 1 is worse than the other 3 fine...replace the injector or clean it
if it prooves more than 1 are not same and 1 is worse or more...
clean the injectors
clean the rail
clean the fuel filter
clean the lines to the tank
and test the fuel pump
no improvement ..faulty pump.
remeber you dont need head gasket to blow in water jacket or oil port
sometime they go cyclinder to cyclinder
or cyclinder to outside.
so compression test the cyclinders cold, same amount of turns
then with sqirt of oil , in cold
and note what each is...more than 15-20psi differnce in any ..is a problem
first off rule out the obvious by doing a full tune-up, this is fuel filter, spark plugs, plug wires, pcv valve, and air filter. if its still rough after that, go buy a can of "SEAFOAM" engine treatment. follow the instructions which say to put 1/3 of the can in the gas tank, 1/3 in the oil and suck 1/3 into the vaccum line that feeds the injectors, shut off car and let the treament sit in there for a while, i let mine sit for atleast 1 hour before proceeding. then after that, crank the car up and rev the motor continuously or drive it hard until the smoking that comes out of the tail pipe goes away, that should strip any carbon off the pistons and clean off the injectors and leave the 1/3 in the oil to clean the crapp out of the motor. it says use 1/3's but i usually put 1/2 can in my fuel and 1/2 in the oil to clean better and 1/3 of another can in the vaccum hose. if you need more info on how to do it look up how to seafoam on youtube