88 MJ Comanche failed CA smog high CO - JeepForum.com
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Cherokee & Comanche Forums > MJ Comanche Technical Forum > 88 MJ Comanche failed CA smog high CO

The Original 3/8" Ruffstuff Diff Cover!Ruffstuff Axle Simple Swap Kit!The Ruffstuff NOT Universal 4 Link Kit!

Unread 08-10-2013, 03:12 PM   #1
Registered User
Join Date: Aug 2013
Location: san luis obispo, CA
Posts: 3
88 MJ Comanche failed CA smog high CO

88 Comanche 4.0 i6 just failed smog for torn PCV line, torn evap line and high CO. Acceptable CO levels are under 1.00% @ idle and @ 2500 rpm. My MJ scored 2.08% @ idle and 1.59% @ 2500 rpm. Any suggestions? I was thinking about replacing only the O2 sensor MAP sensor and spark plugs. Could I possibly pass by only replacing the torn PCV and evap lines?

sbwell1020 is offline   Reply With Quote Quick reply to this message
Unread 08-19-2013, 09:27 AM   #2
Registered User
1984 XJ Cherokee 
Join Date: Aug 2013
Location: acworth, ga
Posts: 31
HC: Unburned Gasoline
CO: Partially Burned Gasoline
CO2: Completely Burned Gasoline
O2: Oxygen, the Good Stuff
NOx: Oxides of Nitrogen (This is only seen by a 5-gas smog machine)

HC: misfire or bad burn
CO: too rich
CO2: engine efficiency
O2: too lean or just air
NOx: too hot or too lean

High CO means you are running too rich to pass. That means you need to lean it out a bit, which could be done by replacing the O2 sensor, etc. Did you have them run it in 'test mode' to check it before the actual run? That tells you all the numbers above, but doesn't 'cost' you to run it (most shops will run it in test mode if you ask them). Then, you look at what it fails on, make a quick adjustment, run test mode again, and if it passes in test mode, you have them run it for real and it'll pass.
CmpleteCherokee is offline   Reply With Quote Quick reply to this message

Quick Reply

Register Now

In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.
Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.

Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Thread Tools

Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.