89 Cherokee 4L. Just bought from a PO who lived where emissions was not needed so to get the title transferred it has to pass emissions. Took it through as it was and it just barely failed for Idle CO. limit is like 1.20 and it had 1.68.

so started with basics and did a full tune up. Plugs, cap, rotor, wires and air filter

took it through and it failed again, but worse than before, it was up to 1.85 instead of 1.68.

so what's next? the EGR vac. hoses seem to be a bit of a mess but not sure how much that would effect it, they are all hooked up just not sure if its right. 02 sensor? seafoam and GTP (guranteed to pass)? up for any options, sharing 1 car sucks! haha

 

Why dont you check out your pcv valve, everyone misses that on a tune up. besides its like 10-15 bucks, next look at ALL of your vacum lines, how does it idle? if it idles too high or low thats an indication that your loosing vaccum. You have a lot more that runs off of vaccum than you think, if you have cruise control, that runs off of vaccm, and so does your brake booster


oh yeah, remember when you go to the parts store, their computer doesnt reconize our PCV valve. you have to say "Pcv valve vaccum line" it will be the whole line.

Dont get carried away, remember KISS
Keep It Simple Stupid.
good luck