smog fail, calling so cal Mark!

[kauboi]

So, been getting a bunch of maintenance done on my out of long term storage 84, including;
Valve adjustment
new O2 sensor
oil vapor recycler clean/hose replaced
clean and gap plugs
vacuum advance replaced
all fluids, and filters
timing belt
strobe timing
idle at 950 rpm
Thermo time checked out OK


I realized that back when I got the car, in '98, I loosened the air flow meter spring...d'oh!, so after failing the smog test, I've bought a replacement. I had been smelling what I thought was just old gas fumes, but now think is a rich condition. I also found my cold start injector to drip a little instead of spraying at cold start, but NOT drip while running. I rigged up a battery and "shocked" it several times and now have a nice spray, and again, no drip. I bought a new temp sensor but it reads very closely in resistance to my original, though I'll install it with the "new" AFM. I also did not drive a lot before the test, though long enough for a few fan cycles.Anyway, here's the results.


I'm just hoping it's not dripping or bad injectors, as I'm near my limit with the car right now.

[So Cal Mark]

it's not a rich issue and unfortunately you've made the issue worse by replacing the vacuum advance. Nox is your big issue and it's created at high cylinder temps. So, if the mixture is too lean, Nox goes up, if the timing is advanced, Nox goes up, if the engine temp is high, Nox goes up. You can't go much richer, if you look at the CO reading you're close to the limit at 15mph. So, if your vacuum advance is now working, plugging it off will help quite a bit. You're allowed + or - 3 degrees from the factory setting, so retard the timing to 7btdc. The vacuum advance has to be connected, but it won't fail the visual test if it merely isn't working.
An easy way to check your fuel mixture is too connect a voltmeter to the O2 sensor lead and adjust the mixture to get a reading of .450 volts.
If you have an infrared thermometer, test the catalytic converter. It should be at least 100 degrees hotter at the outlet than the inlet when running at rpm above idle

[kauboi]

thanks for the reply, I'll try the timing and when I retest, the vacuum, uh, fix. I think I'll compare the O2 sensor voltage before and after the AFM swap as well, and measure the inlet/outlet temps on the cat. Thanks again!, I'll post the results good or bad.

[philbert]

Hi kauboi,

Mark has covered it well and knows a lot more about it than I do, but just wanted you to know that my '84 Pinin spider had similar CA smog fail report and a new cat was the cure.

[kauboi]

Yeah, I'm looking into a new cat as well, though here in California, they make it a bit more costly, so I'll do that as a last resort. Wanna buy a great parts car?

[kauboi]

So, I tested the O2 sensor voltage with my existing afm, and it was around 850mv, played with the screw and got it closer to 4-500mv. Then I tried my "new" used afm, and the readings were very close, making me think my old had been messed with before I bought the car. I held the throttle just above idle and measured my inlet/outlet cat temps, and they are 100 or so degrees COOLER at the outlet....which seems conclusive. Good call Philbert! I'm going to try the citric acid and wood bleach soak with the cat, retard the timing, and plug the vacuum advance, then retest. I'll post results pass or fail.

[So Cal Mark]

if the cat is cooler at the outlet that's a sign it's not working. You might try running it pretty hard to see if it will light off eventually. As cats age they can be quite slow to start working

[kauboi]

so, I put on the acid dipped cat back on, and.......no change..so bit the bullet, put a new cat on and BINGO!
passed the test .The smog guys couldn't believe my cat was original...can post the results pic if anyone wants...thanks guys for the helpful suggestions!!

[philbert]

Glad to hear you are back on the road kauboi!