Here's a fun thing to do -- play with a running engine. So, it rocks a bit. Is it a rythmic miss (pop,pop,pop,pop) or an arythmic miss (pop,POPpity,POP,pittypooopp). If it's rythmic, it is one cylinder missing all the time (Probably ignition or mechanical). If it's arythmic, it's many cylinders missing some of the time (probably fuel/air). If it's rythmic, fire up the motor, pull the doghouse, locate the distributor cap. Ok, here's the fun part -- reach in there and pull a plug wire from the distributor cap of that running motor. Does the rocking get worse? If yes, that wire/cylinder is not causing the original rock. If no, you found at least one cylinder that is not firing for some reason, now stick the wire back on and do the next one until you've gone all the way around. MAybe put some tape on that bad wire so you remember which one it was. There may be more than one bad cylinder. When you're pulling the wire, make sure the rest of your body is not touching a ground, and before you start the motor, pull and replace each wire to make the removal easier when the motor is running. THis also ensures the wires are in, and the distributor cap is tight. Takes about a six pack to do all eight.