Hey all,
My 1998 Cherokee (4.0 6 cyl) Just failed my Colorado emissions.
Hydrocarbons GPM: 1.6497 - limit is 1.2
CO GPM: 9.4488 - limit is 15.0
CO2 GPM: 556.8536
NOx GPM: 1.7761 - limit is 2.50

My gas cap also failed the pressure integrity test. I have a reciept from the previous owners for new spark plugs and wires put on in December of '09.

My question is, if my plugs and wires are fairly new what could the other most common causes be for the high Hydrocarbons number? Are there any other threads with some info that might help? I searched and replacing the cat was mostly all I got. Any suggestions would be awesome, thanks.

 

move to virginia.

 

New rotor cap and spark plugs and the most important is o2 sencer.
09 that was a wile back.

 

Is your check engine light on? Are there any codes that popped up?

 

No check engine light. I'm gonna try to check for some vaccuum leaks today and get a new gas cap. It passed emissions when I bought it a few years ago and since then I have put a header on it, and a new intake, but those are really the only things done to the engine. Some really cold mornings when I start it, it wont stay running unless I hold the gas pedal down slightly and then when it warms up its fine, so I have been thinking there is a vaccuum leak anyways but it seems like for failing on high hydrocarbons it would have to be some thing else. I'm just not sure.

 

*Finish the tuneup with new distributor cap and rotor

*Check for vacuum leaks

*Oxygen sensors can be involved. How many miles on yours?

*Marginal catalytic converter is also on the suspect list

*Be sure that your CCV system is operating correctly and is not clogged

*Verify your fuel pressure. For a 98, you should have 49 psi, plus or minus 5 psi

 

Well I replaced the cap, rotor, plugs, and wires. The cap and rotor were pretty coroded and the plugs looked like crap. The fittings on top of the valve cover have a little bit of oil around them so that makes me think they could be shot. Prolly going to replace them too. This wouldnt be nearly as big of a pain but my tires are too big to fit on the emissions dyno so I have to put it on some 28" rollers to take it over there. I'll have to take a pic of it, it looks pretty funny with those little tires. So if anyone has any other tips on lowering the Hydrocarbons number on my emissions I'm all ears. @tjwalker, I'm not sure how many miles are on the O2 sensors so I may replace them too, I apreceate the tips btw.

 

I would also check/replace the air filter.
Have you tried to run it thru with the big tires?
I know when I take the AMG thru it has wide low profile tires, They won't put it on the dyno, they just run the idle test.

 

an FYI. See Ranger21's name in the upper left of his post?
Right near that is the date of his post. 2012. 12 years ago.

We're working on a fix for this so you are forewarned. welcome to cherokee forum.