96 MONTE CARLO with 90,000 miles, CAME IN FAILED IM240/CE LIGHT ON WITH CODE 133, O2 SLOW TO RESPOND; 300, RANDOM/MULTIPLE MISFIRE; 410, SEC AIR. Found OE plugs, (worn over .060"); likely failed O2. Decal on eng. clip ID'd same engine, but spec'd plug gap at .... Login to read more.