Calif smog test results failed finally passed but don't understand NOX emissions

[icare_dou]

The first legislated exhaust (tailpipe) emission standards were promulgated by the State of California for 1966 model year for cars sold in that state, followed by the United States as a whole in model year 1968. Also in 1966, the first emission test cycle was enacted in the State of California measuring tailpipe emissions in PPM (parts per million). The standards were progressively tightened year by year, as mandated by the EPA.

By the 1974 model year, the United States emission standards had tightened such that the de-tuning techniques used to meet them were seriously reducing engine efficiency and thus increasing fuel usage.

From

Vehicle emissions control - Wikipedia

en.wikipedia.org

So it is not the requirement of when the car was manufactured as I am pretty confident vehicle in CA manufactured from 1968 throug h1974 are currently exempt even thought they had some smog standards. I do have a very vague memory of my parents needing to have a 1971 vehicle smogged. I don't know what was involved. It may have been a visual inspection that the was no after factory modifications.

 

[clinebarger]

Looks like it needs a Catalytic Converter.....Barely passing HC & all.

 

[icare_dou]

Yes the HC is also high but I did not want to do anything to lean out the airfuel mixture when I was actually fail for high NOX. I also had and corrected a EVAP system issue so I might be introducing extra HC via the charcoal canister. I will also acknowledge that the catalytic converter is wearing out as it has 220K miles on it and I think it was my 1985 Park Ave whose converter failed via getting plugged around 120K miles. But the decrease in power was so dramatic it was difficult to climb the hill to get home. I am trying to focus on finding a solution to the high NOX.

 

[Skippy722]

Any oxygen or MAF/MAP sensors could be just starting to fail/get dirty/whatever and be throwing out inaccurate measurements that the computer can work around for now at the expense of emissions.

 

[Chris142]

now you have 2 years to sell it to someone in a state that doesn't require emissions testing on a 94

California requires testing on 76 and newer

 

[Opelman]

The first legislated exhaust (tailpipe) emission standards were promulgated by the State of California for 1966 model year for cars sold in that state, followed by the United States as a whole in model year 1968. Also in 1966, the first emission test cycle was enacted in the State of California measuring tailpipe emissions in PPM (parts per million). The standards were progressively tightened year by year, as mandated by the EPA.

By the 1974 model year, the United States emission standards had tightened such that the de-tuning techniques used to meet them were seriously reducing engine efficiency and thus increasing fuel usage.

From

Vehicle emissions control - Wikipedia

en.wikipedia.org

So it is not the requirement of when the car was manufactured as I am pretty confident vehicle in CA manufactured from 1968 throug h1974 are currently exempt even thought they had some smog standards. I do have a very vague memory of my parents needing to have a 1971 vehicle smogged. I don't know what was involved. It may have been a visual inspection that the was no after factory modifications.

Yes, not that long ago CA required a smog check on change of ownership back to 1955 model year. Cars had to have a pcv system retrofit. 1966 and up got the biannual probe. Cars needed the vacuum advance block off kit and accompanying label on the speedometer. Smog guy was not amused when I rolled up with a 66 Studebaker. Factory 194 GM 6 cyl. The Offenhauser intake with 2 1v carbs was a big fail. Luckily the recurved HEI distributor wasn't worried about. It passed after going back to the stock intake. I was daily driving a 77 Vega in the mid 2000s and getting that smogged was always fun.

 

[ka9mnx]

My bet would be 02 sensor...

 

[icare_dou]

Any oxygen or MAF/MAP sensors could be just starting to fail/get dirty/whatever and be throwing out inaccurate measurements that the computer can work around for now at the expense of emissions.

Very interesting. Back in 1985 or 86 I had a MAF sensor that failed and only acted up after thee engine was operating. The engine would even stop running. I guess it could be running mostly leaner than indicated and a brief moment of richer thus potentially explaining the changing and very high NOX and the almost failing high HC. Is there any testing of a MAF sensor other than a scan tool reading that does seem normal?

 

[icare_dou]

Yes, not that long ago CA required a smog check on change of ownership back to 1955 model year. Cars had to have a pcv system retrofit. 1966 and up got the biannual probe. Cars needed the vacuum advance block off kit and accompanying label on the speedometer. Smog guy was not amused when I rolled up with a 66 Studebaker. Factory 194 GM 6 cyl. The Offenhauser intake with 2 1v carbs was a big fail. Luckily the recurved HEI distributor wasn't worried about. It passed after going back to the stock intake. I was daily driving a 77 Vega in the mid 2000s and getting that smogged was always fun.

Are 1974 and earlier vehicles only required to have smog inspection at change of ownership or also every two years?

 

[Opelman]

Are 1974 and earlier vehicles only required to have smog inspection at change of ownership or also every two years?

Not required at all anymore.

 

[Fabulous50s]

Yes, not that long ago CA required a smog check on change of ownership back to 1955 model year. Cars had to have a pcv system retrofit. 1966 and up got the biannual probe. Cars needed the vacuum advance block off kit and accompanying label on the speedometer. Smog guy was not amused when I rolled up with a 66 Studebaker. Factory 194 GM 6 cyl. The Offenhauser intake with 2 1v carbs was a big fail. Luckily the recurved HEI distributor wasn't worried about. It passed after going back to the stock intake. I was daily driving a 77 Vega in the mid 2000s and getting that smogged was always fun.

Does vacuum advance somehow increase emissions?

My 59 Ford still has the open draught tube and came factory with vacuum advance.

Suprising CA didn't require pre-cat cars to install catalytic converters.

I'd rather retrofit an evap system on the car than put PCV on it, or modify the distributor.

 

[2strokeNorthstar]

Any oxygen or MAF/MAP sensors could be just starting to fail/get dirty/whatever and be throwing out inaccurate measurements that the computer can work around for now at the expense of emissions.

IME CA emissions are so strict, if you fail by a small margin a tune up, cleaning TB, injector cleaning is all a waste of time. You need a new CAT. If you fail horribly you may have extremely old spark plugs or a bad MAF or something.

 

[Opelman]

Does vacuum advance somehow increase emissions?

My 59 Ford still has the open draught tube and came factory with vacuum advance.

Suprising CA didn't require pre-cat cars to install catalytic converters.

I'd rather retrofit an evap system on the car than put PCV on it, or modify

The thought behind the vacuum advance delete was to reduce NoX. Gas was getting crappy and a lot of the older cars with higher compression ratios were having problems with pinging and detonation. Pulling a little timing out helped some but made others run worse like the 250 in my first car, 66 Bel Air.

 

[slacktide_bitog]

IME CA emissions are so strict, if you fail by a small margin a tune up, cleaning TB, injector cleaning is all a waste of time. You need a new CAT. If you fail horribly you may have extremely old spark plugs or a bad MAF or something.

The cheapest California-legal cat for the OP's 94 Park Avenue is this weld-in Walker universal cat. Rock Auto has it by searching the part number 81128. It doesn't show up in the search by vehicle, but it is listed on both Walker's site and California's site

 

[paulo57509]

I remember the days of ignition focused emission control retrofit kits that came after the PCV kits in CA.

Carter marketed one that was an electronic black box that would retard ignition timing until the engine came up to operating temperature; it was wired to the ignition coil with a temperature sensor you duct taped to the upper radiator hose. I see them on ebay every so often.

 

[PandaBear]

I had a car that is also very close to limit, and usually what I do before smog is the cheapest new oxygen sensor (pre cat, about $40 from rockauto) of the same manufacturer (NTK or Denso usually), oil change, new plugs, a good highway run for a while, some Techrons, higher octane gas to avoid knocking or any weird things, etc.

Things that help the most seems to be new O2 sensor, plugs, and oil change.