Emissions failure

[Oizarod115]

went to get my emissions done today and the truck passed on hydrocarbons & NOx but i doubled the limit for carbon monoxide on both the 25 and 15 mph test.

 

the 'pamphlet' on what causes failures in the three areas said to check fuel/air ratios and stuff.

 

in the last year (since i passed the first time) i've gotten

 

all new 5.0 injectors,

fuel pressure regulator,

and maybe adjusted the idle with the screw at the TB once or twice to get it under 1k. but right now it's idling at ~750

 

what should i do to get it to pass?

[JeepcoMJ]

went to get my emissions done today and the truck passed on hydrocarbons & NOx but i doubled the limit for carbon monoxide on both the 25 and 15 mph test.

 

the 'pamphlet' on what causes failures in the three areas said to check fuel/air ratios and stuff.

 

in the last year (since i passed the first time) i've gotten

 

all new 5.0 injectors,

fuel pressure regulator,

and maybe adjusted the idle with the screw at the TB once or twice to get it under 1k. but right now it's idling at ~750

 

what should i do to get it to pass?

 

get a new MAP sensor or mass airflow sensor. that's all it is...the computer isn't getting the correct information to mix the fuel.

[offroader461]

don't worry i feel your pain..lol

i just ran mine through today and passed everything but the NOx...i was barely over limit is 4.50 and i ran a 4.72

 

i 2nd the map sensor replacement...any suggestions on mine??

need help :headpop:

[Eagle]

NOx is usually a product of high combustion temperatures, which can be brought on by a lean-burn condition.

 

What I did NOT see on your list of things replaced is the oxygen sensor. The O2 sensor is a scheduled maintenance item that should be replaced every 80,000 miles. (I use 75,000 as the interval because the multiples are easier to keep track of mentally.) The two most common cause of emissions failure for the 4.0L engine are the O2 sensor, followed by the catalytic converter.

 

[EDIT]Oops ... mis-read your post. So you're okay on NOx but bad on CO. I still wonder when you last replaced the O2 sensor.

[DirtyComanche]

You can always try running it on MEK, acetone, toulene, or methyl hydrate when you go for the test! (don't...)

 

 

It's amazing what people will do to try to pass. I'd assume they do the 15/25 test on a dyno? If so - get some studded tires. They won't run those on a dyno unless they're stupid. At least, in BC(where they do test), they'll let you off with only an idle test if you have them.

 

 

 

I'm lucky, I don't have any of it.

[JeepcoMJ]

don't worry i feel your pain..lol

i just ran mine through today and passed everything but the NOx...i was barely over limit is 4.50 and i ran a 4.72

 

i 2nd the map sensor replacement...any suggestions on mine??

need help :headpop:

 

yep i just bought an nox catalytic converter i forget who it's made by but it's hi-flow and all that good stuff. we converted my 86 from a 2.8 to a 3.8 camaro engine and did NOT put an evap system in it. but it passed well within limits for wisconsin :D

 

the converter was 104.07 or something i'll take a pic and let you know the maker...only some places sell them.

 

other than that you could seafoam it that removes hydrocarbons, or check over your evap system. Unless you have a new cat. though, i'd just do the cat. converter and be done with it.

 

*edit* the catalytic converter was from Catco. 104 dollars or something around that well worth it :D

[Oizarod115]

yeah, it was a 15-25 test on a dyno. apparently my truck weighs 3700lbs... she's a pig. :eek:

 

but i completely doubled the CO limits on both 15 and 25.

 

so lemme get this straight, replace MAP sensor

and if that won't do it replace O2 sensor? or does the O2 only help with NOx...

 

i passed hydrocarbons, but just barely.

[JeepcoMJ]

yeah, it was a 15-25 test on a dyno. apparently my truck weighs 3700lbs... she's a pig. :eek:

 

but i completely doubled the CO limits on both 15 and 25.

 

so lemme get this straight, replace MAP sensor

and if that won't do it replace O2 sensor? or does the O2 only help with NOx...

 

i passed hydrocarbons, but just barely.

 

how good is your catalytic converter? it may be a good idea to start there. I managed to pass with 70 on CO, under 5 on nox and 3.2 on HC by putting the Catco NOX catalytic converter on my truck...with the 3.8 camaro and no evap system. i failed the gas cap pressure test though...got a new one and now i'm good :D

 

MAP and 02 would be a good thing to replace now just to be safe as well. i don't think they're that expensive, but like i said if it's not passing then the computer isnt' getting the correct information to control the air/fuel mixture. so start by eliminating the things you KNOW are good, and work your way from there.

 

with those bigger injectors it will put more fuel in as well. did you compensate by putting a catalytic converter that is up to specs on it?

[Eagle]

If you replace the catalytic converter, you should also replace the O2 sensor, because if the O2 sensor is bad, the amount of unburned stuff going down the pipe will burn out the new cat ASAP. Personally, I would replace the O2 sensor first, and then do the cat if it still fails. If you're fairly certain you need a cat, do the O2 sensor at the same time.

[JeepcoMJ]

If you replace the catalytic converter, you should also replace the O2 sensor, because if the O2 sensor is bad, the amount of unburned stuff going down the pipe will burn out the new cat ASAP. Personally, I would replace the O2 sensor first, and then do the cat if it still fails. If you're fairly certain you need a cat, do the O2 sensor at the same time.

 

good point eagle. i gotta get an o2 sensor on my camaro engine now cause i didn't do that :P good thing i only have a few miles on the new cat :D

[Oizarod115]

with those bigger injectors it will put more fuel in as well. did you compensate by putting a catalytic converter that is up to specs on it?

they're still 19lb/hr injectors, they're just better than the jeep ones

 

so eagle you're stickin with the o2 sensor? :cry: aren't those about 100bucks or so?

[JeepcoMJ]

with those bigger injectors it will put more fuel in as well. did you compensate by putting a catalytic converter that is up to specs on it?

they're still 19lb/hr injectors, they're just better than the jeep ones

 

so eagle you're stickin with the o2 sensor? :cry: aren't those about 100bucks or so?

 

get the o2 sensor. at the same time get a new catalytic converter. you'll spend some bucks but shouldn't have any problems after that. hopefully

[carnuck]

don't worry i feel your pain..lol

i just ran mine through today and passed everything but the NOx...i was barely over limit is 4.50 and i ran a 4.72

 

i 2nd the map sensor replacement...any suggestions on mine??

need help :headpop:

 

Colder tstat and an oil change right before you go in. Engine is running too hot. Another possible is notch the dist so you can retard cam timing slightly or slot the CPS to retard. (I had to do that to cut pinging in mine since I have no EGR)

OH! Do you have an EGR? If it's not functioning NOx will be way up. I also went to NGK plugs for the 2000 Rubicon which cut ping waaay down (which means less NOx is made too)

[carnuck]

CO is unburnt fuel. What plugs are you running? How long before the test was your previous oil change (old oil kicks CO WAAAY up!)

[Oizarod115]

CO is unburnt fuel. What plugs are you running? How long before the test was your previous oil change (old oil kicks CO WAAAY up!)

regular champion cheapies (which is what our trucks like anyways)

and castrol gtx a little over a month and a half ago. should be good on both of those.

[Eagle]

CO is unburnt fuel. What plugs are you running? How long before the test was your previous oil change (old oil kicks CO WAAAY up!)

CO is carbon monoxide. That's not unburned fuel. Hydrocarbons is unburned fuel.

[carnuck]

I meant a byproduct of poorly burnt fuel.

[Oizarod115]

so everyone still agrees on o2 sensor and MAP sensor?

or just o2 sensor?