89 Full size, TBI, 5.7, Auto, 4x4. Did tune up , new plugs, cap and rotor,oil change, filters,etc., new O2 sensor,Base Timing @O, and the HC and CO readings went thru the roof on retest. With new O2 sensor, does the computer need to be reset? If so, How? Could the injectors have failed so catastrophically with new O2 sensor? Sure miss the old carbs!Back to Study Hall! Thanks!
bret

 

Are you sure the timing should be set at 0? Check the emission tag on under the hood. That could be your problem right there.