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240 Just failed CA smog, high NOx

Joined
Nov 22, 2017
Location
California
The results

Already reinstalled the stupid intake preheater. I'll be putting the timing from 6 back to 12 when I do my oil change in a couple days. My cat is a Walker 81111 that's only been on for like 8 months, but probably only gone through 1.5-2k miles, everything in the test seems perfect except high NOx at 25mph. O2 sensor has been replaced earlier this year, spark plugs and wires are less than a year old, and I'm running yellow injectors from an 850. I disconnected the battery for 15 mins to reset the O2 sensor.

Only thing that might have affected the test was that I live not too far from the smog place, so I think I didn't let the car and cat get to proper temps by driving less than 5 minutes. That and my ignition timing was way off.
 
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wennstroma

Active member
Joined
Apr 25, 2006
Location
Idaho
Retarded timing actually helps lower nox.

I don't have experience with that specific cat, but most of the non original ones I saw when I worked down there had to be replaced each smog test to pass on nox (even the small ones Volvo sells now aren't much good). Your gasses make it look like the engine is running okay.

I would advance the timing the minimum amount to pass their check and then drive it over in a low gear to get the cat hot so it has a better chance of passing, and/or see if they'll let you drive it right before they put it on the rollers. If they let it sit and idle for a few minutes, you won't have much of a chance.
 

2turbotoys

Salaminizer
Joined
Nov 13, 2007
Location
Reading pa
I would advise registering the car in a state with realistic emissions laws. Can you register as an antique? That's what I did in PA, no emissions or inspection ever again.
 
Joined
Nov 22, 2017
Location
California
I was reading around and apparently retarding ignition timing too much actually worsened emissions. I'm planning to put it back to 12 since I got the smog check paper right before I bought the car and it passed perfectly back then on 12 degrees, the cat imploded on itself a couple months after I bought it and started driving, so it passed smog 2 years ago on a nearly failed cat.
 
Joined
Nov 22, 2017
Location
California
Yes it's lh2.2. I think timing was the main culprit along with not driving it long enough because I didn't mess with the engine much but replace to newer parts. Exhaust and ignition should all be at stage zero. I don't think anything is wrong with the fuel system, the car starts right up every time. Not sure if the 850 yellow injectors did much, but I have been getting better mileage over time.
 
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IansPlatinum

New member
Joined
Jul 23, 2018
Location
Texas
From engineering school:
V2lCtpEh.jpg


Low HC, no CO and high NOX indicates an overall lean running condition.
 
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ZVOLV

<Master Tech>
Joined
Nov 19, 2002
Location
California
The cat may be no good. Or wasn't lit off yet. Drive it hard and then leave it running when you get to the station.

Another trick is run a good amount of E85 in the tank.

Ignition timing too far advanced will increase smog. There are issues with 2.2 and that vacuum system at the ignition box.
 
Joined
Nov 22, 2017
Location
California
The O2 sensor might not have been working properly too since I swapped out the alternator to a 100A hoping to do an eFan swap in a few days. The battery was disconnected for a while so it may have been reset. I didn't drive it between then and when I did my smog. Would a reset O2 sensor have been what made the car run lean?
 
Joined
Nov 22, 2017
Location
California
The cat may be no good. Or wasn't lit off yet. Drive it hard and then leave it running when you get to the station.
Ignition timing too far advanced will increase smog. There are issues with 2.2 and that vacuum system at the ignition box.

It may have been that I didn't let the cat get to operating temps, I just drove straight from my house to the smog place, less than 5 minutes. I also read in another smog thread, thanks to philski o'flood, that plugging the vacuum line going into the black box on the passenger side fender drops NOx massively because it prevents the system from advancing the timing.
 
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ZVOLV

<Master Tech>
Joined
Nov 19, 2002
Location
California
I recall that post by Philski also. I would go with that.

High octane fuel helps too. I don't know how much Ethanol to recommend, but I would maybe try almost half of the fuel in the tank as E85.
 
Joined
Nov 22, 2017
Location
California
Looking up E85 gas on Google maps shows some pumps near me. Is it fine to mix E85 with 87 gas? I thought you'd need bigger fuel pumps and all that to handle it.
 

ZVOLV

<Master Tech>
Joined
Nov 19, 2002
Location
California
I put about 5 gallons in my 1991 740 Turbo before a smog recheck. I don't have the sheets, but I wanna say it helped.

Those aftermarket cats go bad quickly too. If it really comes down to it, slap on a fresh kitty and it should pass.
 
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