My vehicle failed for the second time. with almost the same readings (78.3910 CO limits being 20.000 and 18.4592 HC limits being 2.000). After the first failed test i tuned it up plugs, wires, air filter, cap and rotor, oil change and fixed a vacuum hose. there are no check engine lights on and the truck runs better than it ever has. before I tested it i made sure it was warmed up I also put super unleaded in the tank about 5 gallons and a bottle of heat additive. Also wouldnt any major component like the cat or oxygen sensor show up on the dash lites. What can I do to lower those numbers it does not seem to be missing or sputtering as it did before i tuned it up?
Apr 18, 2009 at 1:54 PM
