02BlueIS30

My car has 122k on it. I had the 90K service done on time, and 120K service at 118k.

About 2 months ago I noticed a misfire with the engine periodically, but thought it was just bad gas. I put a Chevron fuel injection cleaner in the next tank and used Chevron Fuel and the problem seemed to be gone. Within the next two tanks (shell) the misfile came back. My check engine light came on so I took it in to my closest Toyota dealer (Lexus is far for me). I informed the service writer about the misfire, the check engine light, and my serpentine belt squeaking consistently lately until it was warmed up. They concluded the catalytic converter needed to be replaced, and the tensioner for the serpentine belt. I had the work completed ($2,600). Now the misfire is back. It seems to misfire more when I have the AC on high, verses when its off. Anyone have any ideas what would be causing this to happen? Its periodic and not consistant. If it were consistent I would suspect a bad spark plug. I know a little about cars, but more of the basics.

I just don't want to dump another 1k into this car and would rather get a new one if this repair is going to run that high.

Thanks for any feedback.

02 IS300 Auto 122K