I had a misfire #6 spark plug, I replaced it. It ran good for three months then went bad again...then # 5 had a misfire. I replaced all 6 cop's and spark plugs. still runs bad. the mechanic said it was the # 3 so he swithched the cop's and plugs around and it worked for a day, went into fail safe mode...took it back and he said it was the cat. convertors. I replaced both passenger and drivers side and the FOUR 02 sensors upper and lower...he also replaced the fuel filter...now it shows a #2 misfire and smells like fuel (hope he might of spilled some fuel when fixing and the smell will go away) and he said he doesn't want to work on it any more and has done all he can do...any ideas?