High Nox, smog fail

[Rip]

Im trying to pass a sniff test but fail cuz of high nox. Its got a new cat, egr valve, cleaned egr passages, new cap, rotor, plugs, wires, coil, carb, fuel pump and lines, and filter of course. I have a small pinhole leak in the radiator. Also when i tested it last the coolant was low due to the leak. Could this make it run hot enough to cause failure? Ill find the results and post them.

[Irish_Alley]

Don't know about your state. But in DE if you put "X" amount of money into the truck for emissions than they will pass you

[Rip]

Here in Ca i think you can get an exemption if its gonna cost $600 or more. Its a 1980 Big 10, 350, 4  bbl, egr. Ive read to dial back the advance to lower nox but it went up 800 ppm with 2 degrees. Ive also read  a lean mix can cause high nox, but the smog tech said it was rich. I have it thinned out a bit and at the shop now...

[Irish_Alley]

was this at idle or 2k?

[Rip]

It tests at 15 mph and 25 mph, 15 is at 1285 rpm and 25 is at 1454 rpm. I have a new cat and egr valve. I had cleaned out the egr passage in the intake manifold when i had that off. Tonight i finally put a vacuum tester gauge on the line going from the egr valve to the thermal vacuum switch by the thermostat housing and it was dead. Even when up to 2000 rpms. I checked the line from that switch to the carb and it had 10 inches at 2000. The other lines coming out of the switch, one of which also goes to the carb and the other to the charcoal can, are also without any vacuum. Im thinking the switch is bad and never even opening the egr valve.

[VileZambonie]

Post all of your gas readings please

CO CO2 HC O2 NOx

[Rip]

I changed the vacuum switch but it still gives no vavuum to the egr valve.

[VileZambonie]

Look at all that O2...Check for a vacuum leak

[Rip]

The carb i have i think is a M4MC. There is a ported  vacuum switch that has four nipples in a square pattern . One hose goes off it to the trans conv lock up switch. Another hose splits between the egr valve and the  charcoal can. The other two come from the base of the carb but only the one on the driver side has vacuum at 2000 rpm. The one on the passenger side gives a little at 3500. Does the one on the pass side only give vacuum at high rpms to lock up the conv and this was hooked backwards before?

[VileZambonie]

Post a pic of what you are describing and are you certain the EGR is functioning as well? Do you have a vacuum gauge?

[Rip]

Carb and egr valve are new, hoses and ported vacuum switch (black with red dots on top) are as well. Ist pic shows everything but the air cleaner. 2nd pic shows ported vacuum source off front of carb on driver side to ported thermal vacuum switch. At idle it had no vacuum but goes up to 10 inches around 1500-2000 rpms. 3rd pic shows the vacuum source on the passenger side of the front of the carb. It pulled nothing at idle and maybe 5 iches at 3300 rpms. The hose with the 90 degree elbow goes to the converter lockup switch. The hose that goes into a Y goes to the egr valve and the port on the charcoal can that says main vacuum. This seems correct to lock up the conv at higher rpms and open the egr.

[Rip]

Well it passed smog but id still like to tune it better... Im not sure if i have the catb tuned right.

[VileZambonie]

You can simply hook the vacuum gauge up to the EGR hose (tape the gauge to the windshield) and drive it. At operating temp while cruising you should see it pull a vacuum. Nevertheless you are saying it passed so what changed?

[Rip]

I hooked the egr valve hose to the stronger vacuum source on the carb to open the valve. Thats why it seems somethings not right on the carb, it seems both should have the same vacuum...