I have a nissan sti 94 model, the car suddenly started misfiring. on 1994 Nissan Sentra

Car is mis firing when idling and when accelerating the fuel consumption is very high. What can be the problem?

Asked by for the 1994 Nissan Sentra
review when last tuned up. it may be due.
rec. fuel system clean. ethanol treatment to 1 tank of premium fuel. ethanol blend in fuel causes build up in fuel system, combustion chambers, exhaust system and causes increased wear to spark plugs.
rec. oil stabilizer treatment with next oil change. recondition cylinders and seals(improve compression).