Every few years I chime in on how I am getting Jeeps to pass smog. For reference I have been in the industry 10 years, I work at a STAR station in So Cal and I have a huge jeep customer base along with owning one myself.
Whenever a jeep fails, it seems everyone and their mother starts throwing everything and the kitchen sink at a jeep... TAKE A DEEP BREATH, lets walk through this... I have recently had 3 failures all yj's and I wanted to talk to you about what fixed them, and how you SAVE MONEY.
1st yj 1994,4.0, 5spd fails for high nox.. 2,000 and HIGHER 15mph, 25mph. HC, CO all low well within limits. vehicle has 187,000 miles on it. perform a chrysler top end cleaning (better version of sea foam) nox drops to 1,000 NOX at 15, 880 at 25. Notice the temp gauge is running 210 with long swings to 150 and back. Client says they have never replaced thermostat. Replace thermostat, engine steady at 185-190. passes test 15mph 450 NOX, 13 HC, .07 CO, 25mph 550 NOX, 16 HC, z.02 CO
remember NOX is a product of heat. as cylinder temps rise, so does NOX, so you want to make sure you have your jeep running at the proper temperature, also these 4.0's build carbon like crazy, BUT people sea foam them WAY TO OFTEN. If you had 40,000-100k, and you are running warm on NOX, than maybe sea foam it, but the people who sea foam every 10,000 miles you gotta think A) you are running sensors as you run caked up gunk past everything.. 02 sensor, cat, its great for the once and a while stuff, but unless you have 100K or more, or need a hail marry 40,000 miles clean, I dont recommend the stuff. 4.0's build carbon, carbon builds heat, heat builds NOX, if you dont have carbon, you dont need sea foam.
Jeep 2 4.0 5 spd, NOX 1530 15mph, 900 25mph. HC, CO all within spec. New complete exhaust system from magnaflow INCLUDING CAT. Banks header. This one was a mind boggler, cause how the hell do you condemn a brand new cat? new 02 only raises NOX. Customer claims to sea foam before bring it in. Customer has taken it to multiple shops, none can get it to pass. LETS TALK EXHAUST LEAKS.... if you have 3% oxygen entering the exhaust system ahead of the cat in ANYWAY, cracked header, burned exhaust gasket, ETC. the oxygen renders the cat useless for clean up NOX. Remember the new exhaust? It was a really nice kit supplied with exhaust clamps.... Weld entire exhaust into place, after running multiple tests we found a HIGH amount of oxygen in the system, putting our hands up to the exhaust you could feel an exhaust pulse no matter how tight the clamps got... Once welded. NOX was 100 and zero (15,25)
3rd Jeep. 4.0, 5spd, customer brings jeep in, jeep fails NOX 1100 at 15mph, 1970 25mph, HC and CO all relatively low HC 30, CO .07. Customer says he put an 02 in 4 months ago to get better gas mileage, has since gotten WORSE gas mileage and has to run 91 to stop pinging. Customer Sea Foamed 20,000 miles ago. last 2 smogs vehicle has always passed no problem. Customer replaced 02 with factory chrysler unit. There is something to be said cause the factory sensors are no longer working properly for us, they are all lean biased in the last 4 jeeps I have had to put 02's in. I found the original supplier use to be NGK, but sometime in the last 2 years the 02 sensor itself changed in appearance and ever since then I have had 02 problems with new out of the box units. All I did was through in the NGK 23023. HC 13 CO .02 NOX 650(15) 400 (25).
So just a heads up for you poor bastards that need to smog LOL
Whenever a jeep fails, it seems everyone and their mother starts throwing everything and the kitchen sink at a jeep... TAKE A DEEP BREATH, lets walk through this... I have recently had 3 failures all yj's and I wanted to talk to you about what fixed them, and how you SAVE MONEY.
1st yj 1994,4.0, 5spd fails for high nox.. 2,000 and HIGHER 15mph, 25mph. HC, CO all low well within limits. vehicle has 187,000 miles on it. perform a chrysler top end cleaning (better version of sea foam) nox drops to 1,000 NOX at 15, 880 at 25. Notice the temp gauge is running 210 with long swings to 150 and back. Client says they have never replaced thermostat. Replace thermostat, engine steady at 185-190. passes test 15mph 450 NOX, 13 HC, .07 CO, 25mph 550 NOX, 16 HC, z.02 CO
remember NOX is a product of heat. as cylinder temps rise, so does NOX, so you want to make sure you have your jeep running at the proper temperature, also these 4.0's build carbon like crazy, BUT people sea foam them WAY TO OFTEN. If you had 40,000-100k, and you are running warm on NOX, than maybe sea foam it, but the people who sea foam every 10,000 miles you gotta think A) you are running sensors as you run caked up gunk past everything.. 02 sensor, cat, its great for the once and a while stuff, but unless you have 100K or more, or need a hail marry 40,000 miles clean, I dont recommend the stuff. 4.0's build carbon, carbon builds heat, heat builds NOX, if you dont have carbon, you dont need sea foam.
Jeep 2 4.0 5 spd, NOX 1530 15mph, 900 25mph. HC, CO all within spec. New complete exhaust system from magnaflow INCLUDING CAT. Banks header. This one was a mind boggler, cause how the hell do you condemn a brand new cat? new 02 only raises NOX. Customer claims to sea foam before bring it in. Customer has taken it to multiple shops, none can get it to pass. LETS TALK EXHAUST LEAKS.... if you have 3% oxygen entering the exhaust system ahead of the cat in ANYWAY, cracked header, burned exhaust gasket, ETC. the oxygen renders the cat useless for clean up NOX. Remember the new exhaust? It was a really nice kit supplied with exhaust clamps.... Weld entire exhaust into place, after running multiple tests we found a HIGH amount of oxygen in the system, putting our hands up to the exhaust you could feel an exhaust pulse no matter how tight the clamps got... Once welded. NOX was 100 and zero (15,25)
3rd Jeep. 4.0, 5spd, customer brings jeep in, jeep fails NOX 1100 at 15mph, 1970 25mph, HC and CO all relatively low HC 30, CO .07. Customer says he put an 02 in 4 months ago to get better gas mileage, has since gotten WORSE gas mileage and has to run 91 to stop pinging. Customer Sea Foamed 20,000 miles ago. last 2 smogs vehicle has always passed no problem. Customer replaced 02 with factory chrysler unit. There is something to be said cause the factory sensors are no longer working properly for us, they are all lean biased in the last 4 jeeps I have had to put 02's in. I found the original supplier use to be NGK, but sometime in the last 2 years the 02 sensor itself changed in appearance and ever since then I have had 02 problems with new out of the box units. All I did was through in the NGK 23023. HC 13 CO .02 NOX 650(15) 400 (25).
So just a heads up for you poor bastards that need to smog LOL
