i have a 99 mercury cougar ive had for about a year n a half i had a problem with my check engine light like 2 days after i bought the car and got it checked and they said it was my oxygen sensor so i went and got it fix but after i got it fixed the light came on again for like about 1 to 3 hours,then it went back off, so now its happened again a year later and auto zone is telling me that its my catalytic converter because a code po420 keeps popping up and it says something about cylinder 1 isnt performing correctly and something about a OBDII , i just wanted to find out if this is the problem or do i just need a tune up, cause i havnet got a tune up on this car yet ever since i bought it because i just havent had the money for it , i bought some spark plugs the other day for it and i was gonna see if that works, soooo somebody please tell me what should i do , cause im really having a hard time finding a catalytic converter for this car , theres none avalible in the local stores
