I started my car the other day and it started shaking like it was gonna stall or grew a nice cam overnight. There was a loud clanking around the header/cat. The check engine light went on, but a test drive made it seem like it was ok. I check the plugs, and then took it to Advance Auto for them to check it out for free(very nice).
They said it was the O2 sensor reading high voltage, i forgot what number, but the drivers side before the cat, reading A/F ratios.
What does this mean? did the gas man put some shitty fuel or 87 into my car last time i tanked up? is my tune thats meant for 93 now having a fit.
Help appreciated. thanks.