Hello All,

My 89 4.2L YJ just failed its smog on HC, results as follows...

15mph MAX 124 AVG 34 MEASURE 125
25mph MAX 104 AVG 23 MEASURE 104

As you can see it was a real close one, it was well below average on CO
and NO.

I should have put two and two together as I noticed the other day some
soot build-up on the tail pipe. SO my question is beyond changing the
PCV valve, an oil change, and high octane gas, is there anything else I
can do? I changed the PCV valve, distributor cap, rotor and ignition
wires three months ago, do you think changing the sparks would help
any?

Thank you in advance for your time and consideration of this matter and
your replies.

Cheers, kind regards,
Steve