I have a 1989 4 runner that won't pass smog. Ive replaced the mass air flow sensor , the TPS ,cap & rotor,spark plugs PVC valve and a BOSCH universal O2 sensor. I have also run injector cleaner thru the gas tank & checked the EGR system and it is working. The smog check was - @ 2500 rpm the limit for the HC ppm 220 and the truck read 90 (pass) the CO% limit is 1.20 the truck read 1.16 (pass). The idle test @ 796 rpm is HC ppm limit is 220 the truck read 253 (fail) and the CO% limit 1.20 and the truck read 4.44 ! (fail)!!! . What could cause this ? should I bump the idle speed up to 1000rpm ? Would retarding the timing 2 deg help ? Any help is welcome . <img src="/forums/images/graemlins/confused.gif" alt="" />