CA smog test failed

[greenspider]

80 FI - Well, failed my CA smog test, first time ever since the 80's. CO too high but not terrible, but big difference from the last biennial. The car hasn't been driven much ("under restoration'') and no adjustments other than cleaning AAV were changed. Also sprayed carb cleaner around vacuum hoses without finding any leaks. Changed oil, plugs, checked K&N air filter, and set ign timing to 9-deg/ idles just shy of 1000rpm when warm. Frankly, the engine starts right up, idles smoothly and pulls strong. However, it did exhibit an overrun spasm and loud bang once during warmup driving before the test, but not during the test.
Smog tech said possible O2 sensor or cat which is original. Any thoughts on why the big difference from 2000 test? Obviously the culprit is unburnt fuel, possibly CSI, leaky injectors, restricted fuel return line, AAV? I also noticed that it swooshes, releasing pressure when unscrewing the fuel cap. Is this typical? I have the Factory shop manual, FI diagnosis manual and read through the posts. I don't have access to an exhaust analysis so I'll rely on other methods when diagnosing. Id rather not mess with the AFM as nothing has changed. Any suggestions on where to focus first? Maybe a rat in the cat. Thanks, Tony

[greenspider]

I'm not sure if image of test results posted.
CO% 15mph 25mph
Max 1.43 1.23
2022 2.69 1.16
2020 0.06 0.23

[18Fiatsandcounting]

Good to hear from you, Greenie!

Since the change between 2020 and 2022 was pretty dramatic, that would tell me that it's likely NOT the catalytic converter or the oxygen sensor, as these tend to "fail slowly." Especially since you drove it very little over the past 2 years.

The first thing I would do is test it again, but this time get the catalytic converter stinking hot. Test immediately after this, and don't wait an hour for the next opening in the shop's schedule before testing, as it will cool back down again.

My '93 Jaguar has this problem. Passes just fine when tested fully warm, but fails if the engine has only been warmed up 5 or 10 minutes.

So, see if you can find a smog shop that will work with you on this and get the engine fully warmed up and then test right away.

-Bryan

[greenspider]

Thanks Bryan. I trust the smog tech but I think I’ll try a different shop and do as you suggest. I was skeptical of the failed test and should of have had another done right away to be certain. Should the gas tank release pressure when removing the cap? I didn’t notice this happening previously. Tony

[18Fiatsandcounting]

Should the gas tank release pressure when removing the cap? I didn’t notice this happening previously.

Do you think it's pressure building up inside the tank, or a vacuum? I know my '71 spider builds up a little bit of a vacuum over time (not much), but it doesn't seem to affect the running.

I don't think there should be much pressure (or vacuum) in the tank on an FI spider. Might be something to look into, and perhaps someone here has a better idea of what could be causing this. The simple solution is to just leave the gas cap cracked a little bit, although the smog techs don't like to see this.

-Bryan