Failed smog test for high nox

Have you done live data on your O2s? I wouldn't replace them without codes or voltage over .9v.

Seafoam is cheap. Do it!

My money is on cracked exhaust headers.

-Mac
 
That stinks, that is for sure. I’ve never used Seafoam but heard a lot of others try it. So guess I am with Mac, if it’s cheap might as well give it shot. Are they charging you for the retest?
 
macleanflood said:
Have you done live data on your O2s? I wouldn't replace them without codes or voltage over .9v.

Seafoam is cheap. Do it!

My money is on cracked exhaust headers.

-Mac
Click to expand...

Here's some live data pulled last night, looks like the O2 sensors are at .7 and. 6v roughly?

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Danarch said:
That stinks, that is for sure. I’ve never used Seafoam but heard a lot of others try it. So guess I am with Mac, if it’s cheap might as well give it shot. Are they charging you for the retest?
Click to expand...

I got the first test for free as a favor from the guy, but I paid this morning for the official test (which I failed).
 
Pulled the tstat, here's a photo, I don't see anything clearly identifying whether it's a 195 or not, anyone able to tell?

Edit: maybe the 80 stamp refers to the temp in Celsius which equates to 176f? So maybe a 180 degree tstat?

Second pic is the stant 195 I just got with the weep hole drilled per several posts I've found on here in other threads.

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Last edited:
Well here's an update on my situation and additional steps taken which resulted in another failed test this morning. 😭

Swapped in the 195 tstat last weekend. I also ran a bottle of sea foam through the brake booster line. I also bought some fuel injector cleaner and a product called Guaranteed to Pass from CRC, it didn't pass lol.

The guys at the test station suggested pulling the plugs to see if it's running rich or lean, and then trying to solve for that condition before throwing more money at a new cat,O2 sensors etc. I've also got a slightly high idle that may be part of the problem, it idles around 1000rpm while in park or neutral.

I've tried finding a vacuum leak by spraying carb cleaner at the vacuum line connections throughout the engine bay with no luck. I'm not confident tho that that means there isn't one, but are there other possible causes for the high idle I should be investigating? IAC? TPS was replaced about a year ago with a Mopar already.

I guess my next steps will be to pull the plugs and see how they look, they were replaced about a year ago with the xp985s recommended here...sigh

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But did you get double your money back?

I test thermostats is a pot of water on the stove using a thermometer.

You check your vacuum reservoir under the battery? Or get some caps from the auto part store and cap off the line running to the HVAC.

-Mac
 
macleanflood said:
But did you get double your money back?

I test thermostats is a pot of water on the stove using a thermometer.

You check your vacuum reservoir under the battery? Or get some caps from the auto part store and cap off the line running to the HVAC.

-Mac
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Haha, I'll have to look into that guarantee.

Regarding the vacuum reservoir, I did get under there and spray carb cleaner where the vac line connects, with no sign of a leak.

Regarding the HVAC line, can you elaborate on why you think I should cap it? Last year I replaced my timing chain and to make room for the job I disconnected the AC compressor to move it out of the way, so my AC hasn't worked since then because I'd need to get it refilled. Not sure if that might mean you're on to something there or not...
 
macleanflood said:
Can't spray carb cleaner at all the vacuum actuators and lines...so cap it off and see if it fixes the idle.

-Mac
Click to expand...

Last night I sequentially capped off 1 vacuum line at a time where the 3 nipples are on the side of the intake manifold while the engine was running. As I capped each of the lines there was no change in rpm which in my mind tells me that I don't have a leak in any of the vacuum lines that are down stream of each of those nipples. Does this logic sound correct? I also pinched the brake booster line and no RPM effect there either which I think rules out an internal leak in the brake booster.

If the above is valid, then my plan today is to do a diy smoke test as I'm now suspicious that it might be a leak at the manifold gasket possibly.
 
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williambmac said:
With 192k miles, it probably needs a catalytic converter. If you have access to a borescope, remove one of the O2 sensors and see if there is any material left in the cat.
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It's already got an aftermarket cat in it of unknown age, which your right, likely will need to be replaced.

What I'm trying to do first tho is diagnose and resolve my slightly high idle which I suspect is causing the motor to run rich. If I don't solve that problem first, the new cat isn't going to last long.

Today I was researching short and long term fuel trim and how to interpret results. I was monitoring live data in my driveway and the long term fuel trim was slightly negative around -0.8%, so slightly rich, but from what I've read is well within tolerable limits. One other interesting thing, I read you can diagnose a possibly faulty O2 sensor by disconnecting a vacuum line and the shirt term trim should immediately become positive indicating a temporary lean condition. When I did this, it had no effect on short term trim. So it's also possible my O2 sensor isn't working properly?

I would greatly appreciate other thoughts from anyone knowledgeable on fuel trim and diagnosing engine problems based on these results!
 
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