I have a 98 integra and for the last year it has ran rich.
it doesn't blow smoke, but around the tail pipe and bumper there is soot. 6 months ago the chk engine lite came on and it was code 420. the catalytic system/vacuum leak/02 sensors.
i replaced the 02 sensors in front and replaced the converter. the lite went away and the next day i had an emissions test and it passed!
now yesterday the lite came back on and it read the same code.
there is still soot being pumped out the exhaust and it is burning rich?
what do you think might be causing this??