I'm not sure, probably not. 192 is still lower than normal/recommended though.
One more thought, has your engine ever pinged causing you to need to run higher octane gasolines like 89 or 91 to stop the pinging?
Failed smog test for high nox
- Thread starter GregBelleville
- Start date
One more thought, has your engine ever pinged causing you to need to run higher octane gasolines like 89 or 91 to stop the pinging?
OP
Ok, well it was worth asking. No, never had pinging issue.
For now my plan is to inspect for exhaust leaks ahead of the cat and to inspect the vacuum lines as thoroughly as possible for a leak as I also have a high idle to solve for.
OP
I leak tested the exhaust today by blowing air through the tail pipe with my shop vac. Only leak I found ahead of the cat is at the manifold to the exhaust pipe flange. I believe the FSM says torque spec for these flange bolts if only 23 ft lbs? I checked both bolts and they were already at or exceeding 23 ft lbs.
Am I wrong on this torque spec? I don't want to break a bolt, but I also need this leak to go away.
Am I wrong on this torque spec? I don't want to break a bolt, but I also need this leak to go away.
I've never had anything but trouble with those donut seals. Really been thinking about using a healthy coat of high temp RTV like Permatex Ultra Copper.
Might just want to start with a new donut seal.
Oh, and my exhaust kept loosing up...that would in turn let the seal errode and the chunks ended up in my CAT.
-Mac
Might just want to start with a new donut seal.
Oh, and my exhaust kept loosing up...that would in turn let the seal errode and the chunks ended up in my CAT.
-Mac
Can you unbolt the muffler from the cat?
If so a flashlight into the rear of the cat will help you know if its intact
If so a flashlight into the rear of the cat will help you know if its intact
You are correct,NOX is related to high combustion temps around 2200 degrees so a thermostat won’t fix it. Nox usually timing, lean condition, egr or Cat related. I would suspect the cat. One technique I use is keep the engine running at the smog shop then hold the rpm around 1500 rpm for a couple minutes right before they put it on the dyno. This will keep a weak cat up to operating temperature where it might clean the Nox up enough to pass.
Great idea on blowing air through the tailpipe. I suppose could do the same for a smoke test? My hearing isn’t the best so sometimes hard for me to tell the sounds. I plan on getting a smoke machine some time.
OP
I would like to get this flange sealed properly and retest it to see if that improves the NOX. From what I know, any leaks prior to the cat will cause NOX to increase. I want to rule that out as a cheap solution before spending big money.
If you have an infrared thermometer you can check inlet and outlet temperature to see if the cat is working outlet should be hotter than inlet.
OP
OP
Hmm,i thought an exhaust manifold leak would fool our motors into running rich,not lean.
OP
I found this post from another forum from a smog tech, brand new exhaust system that was leaking at the clamps. Once the leak was resolved the NOX levels came down:
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)
OP
Hey Mac, if you were going to use high temp rtv to seal this flange, how would you go about that? Line both sides of the pipe with it before replacing the donut seal?
Probably dope up the donut real good, plop it in and finagle it into place as I tighten the bolts.
-Mac
I agree. But I went through three gaskets and replaced the header and mid pipe. All mine leak just enough to cause the OP's issue. Luckily for me no smog test in OR.
Next time I have mine apart I'll probably try what I'm suggesting...but again...no actual experience.
Probably should just cut off the donut flanges and replace with a v band...but I don't want to void my Banks header warranty because I'm guessing I'll need it a few times.
-Mac
OP
Like it or not I went with your suggestion Mac. I'm going to let this cure tonight and then take it back in for a retest this week hopefully and see if that solves it or if I move on to the cat.
OP
Ok, it's been a couple weeks, but I retested the Jeep this morning and it failed again due to high nox and high carbon readings.
All that I've done thus far is seal up the exhaust leak I had at the flange where the headers meet the exhaust pipe. I wasn't too hopeful that simply sealing that leak would get me to pass because that would be too easy and inexpensive right?
He suggested sea foam treatment, O2 sensors, and replacement of the catalytic converter as additional steps. He also said he knows a "guy" if I can't get it to pass, so there's that as well, but if really prefer to solve this problem rather than kick the can down the road.
One other option I'm investigating is my thermostat because my coolant temp seems to be running on the lower side at around 190 degrees rather than at 210. As I understand it, the engine running cool could cause carbon buildup and a rich condition? Anyway I have a stant 195 tstat coming today which I'm try to swap in over the weekend. This is going to start getting expensive quick though if I replace the O2 sensors ($135 each for Mopar on rock auto) and possibly cat back exhaust as well...
I'm open to other ideas though if there's something I haven't already mentioned other than move out of California.
All that I've done thus far is seal up the exhaust leak I had at the flange where the headers meet the exhaust pipe. I wasn't too hopeful that simply sealing that leak would get me to pass because that would be too easy and inexpensive right?
He suggested sea foam treatment, O2 sensors, and replacement of the catalytic converter as additional steps. He also said he knows a "guy" if I can't get it to pass, so there's that as well, but if really prefer to solve this problem rather than kick the can down the road.
One other option I'm investigating is my thermostat because my coolant temp seems to be running on the lower side at around 190 degrees rather than at 210. As I understand it, the engine running cool could cause carbon buildup and a rich condition? Anyway I have a stant 195 tstat coming today which I'm try to swap in over the weekend. This is going to start getting expensive quick though if I replace the O2 sensors ($135 each for Mopar on rock auto) and possibly cat back exhaust as well...
I'm open to other ideas though if there's something I haven't already mentioned other than move out of California.