blankety-blank echeck!
04-12-2010, 11:36 AM
#1
Seasoned Member
Thread Starter
Join Date: Mar 2008
Location: Mentor, OH
Posts: 349
Likes: 0
Received 1 Like
on
1 Post
Year: 2000
Model: Cherokee
Engine: IL6 4.0
blankety-blank echeck!
Took my '94 XJ to echeck today. It failed on the NOx levels. 1014.0 was the limit and it came in at 1055.8. Anyone know what I need to fix to get it to pass?
04-12-2010, 04:24 PM
#2
Member
Join Date: Sep 2009
Location: Cleveland, OH
Posts: 198
Likes: 0
Received 0 Likes
on
0 Posts
Year: 2001
Model: Cherokee
Engine: 4.0L
04-12-2010, 09:12 PM
#4
Member
Join Date: Sep 2009
Location: Cleveland, OH
Posts: 198
Likes: 0
Received 0 Likes
on
0 Posts
Year: 2001
Model: Cherokee
Engine: 4.0L
04-12-2010, 10:02 PM
#5
CF Veteran
Join Date: May 2008
Posts: 3,018
Likes: 0
Received 13 Likes
on
13 Posts
Year: 1988
Model: Cherokee
Engine: AMC242
Elevated NOx is a product of elevated combustion temperatures. It could also be a sign of a failed/failing catalytic converter.
First thing - get some Seafoam and a catalytic converter flange gasket. Disconnect the converter at the flange, and tie out of the way (the downpipe should be open.) Run the Seafoam through the engine - that should clear out any accumulated carbon deposits, which can (and usually do) elevate compression (and therefore combustion temperatures.) Carbon deposts can also start 'glowing' after a while, which can lead to preignition (and other nasty problems.)
If there's a lot of carbon, that's why you disconnected the catalytic conveter. Shine a light into the converter (to look for a carbon-coated matrix) before you connect it back up - the matrix may have become coated with carbon and that will degrade the efficiency of the thing - and it is sixteen years old (if it's still original.) Retain the flange when you change the converter - cut it off of the old one and have a stub of pipe welded to it. You'd rather have that flange in place, believe me - especially if you have a five-speed!
You've dealt with the carbon now, and you've inspected the cat (and replaced it if necessary.) The only other high-NOx issues I can think of at the moment would be the spark plugs (mentioned - if they're "too hot," they'll retain too much heat and cause trouble,) and the base timing (which should not be adjustable, but can be checked with a timing light. Make sure it isn't wandering, and I am inclined to think it should be 4-6*BTDC (but don't hold my feet to the fire - I'm not sure.))
But, the carbon deposits and the plugs will give you a good place to start. Good luck, and report back if you didn't pass again (with any new symptoms and a history of repairs you've done and noted oddities.)
Make sure your spark plugs are the correct ones for your engine, and aren't "too hot." The retained heat from a hotter plug can elevate chamber temperatures - while this will reduce HC and CO, it will increase NOx.
First thing - get some Seafoam and a catalytic converter flange gasket. Disconnect the converter at the flange, and tie out of the way (the downpipe should be open.) Run the Seafoam through the engine - that should clear out any accumulated carbon deposits, which can (and usually do) elevate compression (and therefore combustion temperatures.) Carbon deposts can also start 'glowing' after a while, which can lead to preignition (and other nasty problems.)
If there's a lot of carbon, that's why you disconnected the catalytic conveter. Shine a light into the converter (to look for a carbon-coated matrix) before you connect it back up - the matrix may have become coated with carbon and that will degrade the efficiency of the thing - and it is sixteen years old (if it's still original.) Retain the flange when you change the converter - cut it off of the old one and have a stub of pipe welded to it. You'd rather have that flange in place, believe me - especially if you have a five-speed!
You've dealt with the carbon now, and you've inspected the cat (and replaced it if necessary.) The only other high-NOx issues I can think of at the moment would be the spark plugs (mentioned - if they're "too hot," they'll retain too much heat and cause trouble,) and the base timing (which should not be adjustable, but can be checked with a timing light. Make sure it isn't wandering, and I am inclined to think it should be 4-6*BTDC (but don't hold my feet to the fire - I'm not sure.))
But, the carbon deposits and the plugs will give you a good place to start. Good luck, and report back if you didn't pass again (with any new symptoms and a history of repairs you've done and noted oddities.)
Make sure your spark plugs are the correct ones for your engine, and aren't "too hot." The retained heat from a hotter plug can elevate chamber temperatures - while this will reduce HC and CO, it will increase NOx.
Trending Topics
Thread
Thread Starter
Forum
Replies
Last Post
XJmayhem89
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
17
01-03-2014 07:46 PM
cherokeefamily
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
6
05-02-2010 06:37 AM
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
