ckeck engin light went off. was the o2 sensor before cat. replaced it. light came back on. went to a dealership they replaced it only a week after i put one in. now only 4 days later it showing the same problem. could there be anything else causing a slow response in the o2 sensor? i need quick help. was getting 350 mpt now only 200 miles per tank.

 

check ur injection system u have 4 of them check them one by one and fuel pumper that may cause that the car uses alot of gas, did u see if the exhaust brings a black or white smoke while driving if yes adjust air and fuel ratio if u have any smoke and check spark plugs that can also make a withdrawal for ur car and that its not to the optimum performance hope that helps..... and just buy original spare parts stamped with hmc (hyundai motor company) that is the most improtant....

saiofa666