Failed emissions

[jctucker]

So, took my recently aquired '79 Spider to get tested a couple days ago expecting the car to fly thru emissions. No dice! (they really tightened the standards this year for pre-1981 cars - fascists!) I got popped for CO% being too high. I'll run down all the readings: HC @ 2500 rpm 186.3 PPM @ idle 205.4 PPM (limit 400)CO 4.52% @ 2500 RPM 3.62% @ idle (limit 1.50%) CO2% 11.5096% @ 2500 RPM 10.9968% @ idle. Oh, it smells fairly rich but runs great.

I realize that high CO is running rich. I replaced the plugs right before I went in. The day after I replaced the plug wires. The air filter looks pretty clean, but I think I'm going to replace it for shits'n'grins.

I've got the stock shitty intake and ADHA carb. Does the Weber ADHA use the idle circuit as also the cruise circuit? I've read somewhere that this is the case. I'm very comfortable with Holleys, Edelbrocks and Quadrajets...not so much with Webers.

Also, if anyone close to Denver has a gas analyzer I can borrow or rent I'd really appreciate it! The shop I work at we do mostly post '90 Audi's, VW's and Porsche's...so we don't have one. Thanks, everyone!

[So Cal Mark]

make sure the air injection system is working and not full of carbon. It's hard to get the carb lean enough if the air pump isn't pumping. You can go to a smaller primary low speed jet and a larger primary air jet. You're running on that low speed jet on the test

[jctucker]

Thanks, Mark. By 'air injection' do you mean the EGR system? My '79 is a non-California model, no air injection pump.

I found the timing was 'several' degrees advanced, so I set it to 10 degrees BTDC. Replaced the air filter (the old one was a lot dirtier than I thought) and the plug wires. Also, I leaned out the idle mixture about half a turn. I'll try to run it thru emissions the next couple days.

It's funny, I bought this car from my boss who said it always flew thru testing. I think when I fixed the half a dozen vacuum leaks it riched up.

[So Cal Mark]

air injection and egr are two different systems and accomplish different tasks. The 79s had air injection; but there are two different systems. One uses a pump the other is a pulse air system. Leaning the mixture screw won't help above idle speed, you need to change the low speed jet or use a larger air bleed, or a combination of the two. In Calif, you're allowed a timing variance of +or- 3 degrees from the factory setting. For the test, I set them back 3 degrees to 7btdc

[jctucker]

Ok, that makes sense. Pulse-system...I'll give it a good go-over.

I'll get a new jet and air bleed. Hurray for tuning carbs at 5500 feet.

Thanks again, Mark!

[jctucker]

Went by for a re-test today and, voila! CO% actually increased from the last test but idle CO% and cruise and idle HCs were well below the limits. So, I'm not sure HOW I passed. Maybe the nice girl who ran my test thought my car was cute.

Thanks for all your help, Mark!

[WBPDX]

I just had a similar experience...

FYI, if your ONLY problem is CO, I have found with other old cars that buying a quart of Alcohol from your local paint store, when added to a gallon or two of gas in your tank, makes an excellent cheat. It will make your car run exceptionally lean from an emissions standpoint. It is terrible for your cat... and you'll probably want to dilute it with more gas immediately after the test.

Sometimes, it is amazing what will pass. My state has similar standards, and my old pickup, which visibly smoked at idle (burning oil, so you would expect high HCs), passed with flying colors on the first try.