sriser

Failed emissions test #1:

High HC (barely out of spec)

Figured since the car was driven about 1000 miles per year and when i got it a few days ago there were cobwebs around the filler cap, I suspected simply that it just needed to be driven with some fresh fuel. Did that. And changed the 02 sensor. Checked timing 6 deg BTDC in Drive.

Failed emissions test #2:

HC was fine, now it was way out of spec on NOx. Crazy.

My thought is to replace the EGR despite it seeming to funciton properly when I tested it. Also changing spark plugs, cap, rotor, AIR pump check valves, air filter, and fuel filter to be changed before next test. My thought is that it is suffering from lean misfire raising cylinder temps causing the high NOx. Could be a clogged fuel filter. Fuel injectors are relativley new and all had 17ohms resistance.

So, anybody have a L98 with high NOx that eventually passed and what did you do?

tbirdsps

I haven't have a problem but you are right on the money thinking there's a lean issue. That will cause high NOX.

kimmer

Acetone in the tank does wonders.

bogus

If the EGR valve was bad, you would know it.

Get a bottle of "Smog chek" from your local parts pimp. That should take care of it.

If not, you are more then likely in need of a new catalytic converter.

sriser

Doing that too. IF it doesn't sqeak past this time, I am going to change out the cats.

GKK

Is the exhaust system stock?...

Headers or larger diameter exhaust pipes will reduce the back pressure needed for the EGR valve to operate correctly.

mike100

Did you actually have to change the ign timing or did you just check it? If you accidentally set too much advance, the NOx will be elevated.

sriser

Passed with huge margin to spare. Spent a grand total of $16. Changed out the AIR check valves on both exhaust banks.

Both were so corroded that they had perhaps 10% air flow. Boom. Done.

bogus

good catch!

PLRX

I didnt know the do "The Sniffer" in Virginia. The virus is spreading from California into all other states.

This is no good, we need a gearhead POTUS.