High NOx, low CO, acceptable HC. Here's my thinking:

- Your spark plugs may be "too hot" - try the next heat range cooler (any competent counterman can help you select the proper plug to do this, and take in the numbers off of the plugs now in there.)
- You're running lean, but the moderate HC mitigates against this thinking.

The fact of having maximum HC allowable at 25mph is interesting - it says you're running rich, but running rich will depress NOx. The extreme low CO was the deciding factor here, in your case (this is why I wanted to see the actual results. I don't care if you redact your name, address, VIN, or what-have-you - what is needed is all of the measured emissions data and the vehicle-specific technical information - mileage and suchlike.)

You are definitely not running lean, since your oxygen emission is measured at zero pecent (if you were running lean, you would have an excess of oxygen, and it would have been measured at the tailpipe.) CO2 looks about right.

I'd want to change the plugs first, and possibly "steam-clean" the chambers - here's how:

- Get a catalytic converter flange gasket (if you still have the OEM flange at the head of the cat) and a spray bottle full of clean water.
- Disconnect the cat at the flange and tie it out of the way.
- Remove the air hose from the airbox
- Start the engine
- At intervals, spray a fine mist of water into the air hose. Every 15-20 seconds is about right.
- Repeat until the black "smoke" stops coming out of the downpipe.
- Shut down engine.
- Reconnect catalytic converter
- Return to service.

HOW/WHY IT WORKS:
The water gets absorbed into carbon deposits on the combustion chamber surfaces. When the fuel/air mix gets "sparked," temperatures in the combustion chambers jump easily by several hundred degrees Fahrenheit. This "flashes" the water into steam, which blasts the carbon loose from metal surfaces. This is what you see as "black smoke" coming out of the exhaust pipe. You disconnected the catalytic converter so you wouldn't coat the matrix with the stuff (it's cheap insurance.)

This is something that is probably useful to do every six to eight years (especially if you run cheap fuel!) and won't harm your engine. Your engine is seventeen years old with ~220K on the clock, so carbon buildup is likely (I just had the head off of a 1990 with ~160K to change a flat lifter & bent pushrod & oil pump, and there was plenty of carbon in the chambers. So, I cleaned it all out - passed smog just fine! NOx was considerably lower than the previous test that had been done on it.)

 

thanks for the awesome post 5-90
im sure it took a min to type it up, and its appreciated.
as you said it takes information to get information.

the thing is, my catalytic converter is welded on.
the smog test/repair shop did it, for whatever reason.

when i had my head off recently (6 Months? maybe) i recall seeing carbon build up, i took a wire brush to it, and cleaned it out the best i could.

instead, i could use a fuel additive to break the carbon build up down?

for now im going to get new plugs.

 

so i took a trip to azone.
and they couldn't identify my current spark plug heat range.
they figured it was 5, and they didn't have any cooler ones available.
and a buddy came by and was suggesting i spray transmission fluid into the intake instead of water. using 5-90's method.
hmmmmm.

 

You can do the water bit without disconnecting the cat - you'll just be blowing more carbon through it than you probably should.

ATF? Yech - I wouldn't. Stick to clean water (tap water is okeh, but you'd be better off with R/O water or distilled.)

Did you check in a different brand for your plugs? There is usually overlap between brands in stock - but some will run to a bit more of an extreme than the others, in some cases. It's worth checking (ran into this when I was working in a parts house years ago...)

Now you understand why I wanted to see all results, yes? Fuel combustion is a set of interrelated chemical processes, and the balance of emissions can point in a certain direction for troubleshooting - even the ones that aren't measured as "harmful" (CO2 and O2) can give useful information when trying to figure out what's wrong, much less the "big three" (HC, CO, and NOx.)

I hope you find my information helpful, tho, and you get past dealing with the Air Police for two more years (did they send you to a "Test Only" station? The third time in a row I had to take my 88 in to a TO I ended up calling CARB to find out why, and they told me it was because I'd been "profiled as a gross emitter." Nevermind that my emissions were consistently close to zero - and would be effectively zero if they'd allow me to modify it. I now "fit the profile," so I get screwed into paying more for the damned test than I do for tags!)

 

i tried spraying water into the intake, and no black smoke came out whatsoever.
and i havn't looked into the spark plug deal again.
i poured 12oz of "guaranteed to pass emission" stuff in my tank.
after i burn this tank up (4 wheelin!) i will test again,
with shroud, elec fan, and 8 o'clock in the cool morning.
that is my plan.

 

well of course you dont have any black smoke. You just did a head job on it, Its not going tohave the carbon build up he's talking about, I just went through this same thing 2 mounths ago with my jeep, Check to make sure you dont have an intake leak that your bottom bolts are tight. They may be but whats it hurt to look.