help catalytic converter possibly

[huyatgr]

My check engine light had been on for a few weeks and while I was in Mexico my mom took my 98 318i in to get it checked out. Our regular mechanic was out of town so she took it to AAMCO to get the transmission serviced and have a diagnostic done. They said my cat converter was contaminated and was effecting my mpg and performance. $400.00 to fix. A few days later the check engine light goes off. When I got back from Mexico I took it to our regular mechanic, who scanned it and No Fault came up for him. Is it worth it to keep investigating this and possibly throw quite a bit of money if the car is still running quite fine and its possible I might be selling before winter. thanks

[Jack Dabsy]

Could be many things, but lets start with the lambda sensors...