Won't Pass Emissions - NOx is Too High

Over the past year, I have been working on my 2000 Subaru Legacy GT Manual in order to get it running smoothly again. It has been sitting since the beginning of January of 2020, and so has the gas. So far I have replaced:

• Headgaskets
  
• Intake Gaskets
  
• Exhaust Gaskets
  
• Main Oil Seal
  
• Oil Separator Plate
  
• Cam Seals
  
• Water Pump
  
• Belts
  
• Spark Plugs
  
• Catalytic Converter Gasket
  

However, when I took it to get emissions done, my levels of all 3 gases were too high, especially with NOx (see images below). I suspect either the gas sitting in the tank for over a year or forgetting to plug in a vacuum line is the culprit. But considering the car has 175000 miles, there's a chance my catalytic converters could be bad. Right now I've put in fuel system cleaner and 91 octane gas after siphoning out the old gas and running it for multiple hours under load. If you guys have any ideas let me know.

What county are you in? They haven't ran dyno's or sniffed pipes where I'm at in almost a year. They just check codes and you pass.

 

You are going to want to get that fuel system cleaner almost all out before you try again. Could have been bad gas. You can try again for free within 25 days.

 

If you don't pass, it may be your cat. good news is cat prices are high right now and you can probably sell your bad one for close to what a new one would be.

 

Any check engine lights or pending codes?

What county are you in? They haven't ran dyno's or sniffed pipes where I'm at in almost a year. They just check codes and you pass.

 

You are going to want to get that fuel system cleaner almost all out before you try again. Could have been bad gas. You can try again for free within 25 days.

 

If you don't pass, it may be your cat. good news is cat prices are high right now and you can probably sell your bad one for close to what a new one would be.

 

Any check engine lights or pending codes?

I'm in Colorado. I guess as of 2021 the state follows the same or similar regulations to California, so there is a required dyno test.

There arent any codes sadly, I'm starting to look at the cats.

I took it to get retested 2 days ago and it failed again. I never thought about selling my old cats, so I'll definitely look into that.

I also found out that the manual version of the third-gen legacy doesn't have an EGR system at all so that would probably explain the super high NOx levels if my cats are bad.

I think I'm just gonna go ahead and buy some cheap new cats off amazon and hope for the best.

 

-Thank you

What county are you in? They haven't ran dyno's or sniffed pipes where I'm at in almost a year. They just check codes and you pass.

 

You are going to want to get that fuel system cleaner almost all out before you try again. Could have been bad gas. You can try again for free within 25 days.

 

If you don't pass, it may be your cat. good news is cat prices are high right now and you can probably sell your bad one for close to what a new one would be.

 

Any check engine lights or pending codes?

I misread your message, I'm down in Lakewood specifically.

Whoops

California just checks no codes and monitors are all registered ok.

They don't dyno the cars after MY 04? Especially a awd car on a two wheel dyno. They did, first time, run the sniffer if I remember back that far.

Last time it was just ECU hookup and visual.

CA, anything that is OBDII just has to pass the ecu test, no rolling road or dyno required.

AWD dyno inspections? Co is pretty tough place, turns out...

I got my cats from Jegs. Direct fit and they are solid.

Get it really hot before taking it in for the test? I found running 20 minutes in 3rd gear before the test and using non-oxygenated gas tended to produce better results. Then again if your cats aren't working (check input and output temps should be about 50F difference) you're kind of stuck

this, ive heard/done it myself have someone watch the shop and make sure there is no line, and pull the car in HOTTTTTT and itll help.

Thank you guys for all of your responses!

I went ahead and got some cheap cats from Amazon and they should arrive soon.

I'll definitely make sure to run them hot and get them up to temperature.

Hopefully, this will fix it, otherwise, I'll keep you guys posted.