Toyota Repair: need help, spark plug wires, distributor cap

Question
i have a 1991 toyota corola awhile ago it started to run really bad it starts fine but when i start to drive it starts to miss,bucks alot.i changed the fuel filter still doing the same thing but getting worse.it has 320000 km. on it  could you please help me

Answer
It sounds like this is an electrical misfire, I recommend that you replace the spark plugs, the spark plug wires and the distributor cap and the rotor in the distributor.
If the spark plugs or the connectors have oil on them the valve cover needs to be resealed, let me know if this helps.