When setting idle make sure your running
on the idle cuircut not main.
keep the rpm at factory spec, as you adjust
air screws and get more rpms, lower idle stop
to spec and tune again, then do 50 rpm idle drop
then up the idle stop 50rpm
good luck

 

Here in "Eco-friendly" Oregon, when my Vette was stock (carb, intake manifold, AIR pump & fuel cannister) all hooked up, I failed. Yep. Failed.

I took off the smog pump/AIR put on a new Edelbrock performer intake & 600cfm carb, tuned it lean & Wha-La! PASSED with flying colors. They ran a mirror under the car to make sure it had a cat, shoved a metering thinggy in the tail pipes and the car passed in 1 minute, no hassles. Like the above posts, this is clearly an ingnition/timing issue and a carb which sounds like it's simply running too rich at idle.

 

Okay, here is what you need to do:

You just barely failed on the HC. The high HC is due to timing being a bit too far advanced, which is typical for a performance level tune on these cars. Check your timing at idle and see if your vacuum advance is hooked up to manifold vacuum or ported vacuum. If you're hooked up to manifold vacuum, simply switch it over to ported vacuum, and this will retard your timing enough to pass. If you're already on a ported vacuum source, retard your timing about 4 degrees from wherever it is right now. Either one of these approaches will require you to re-set idle speed since this will lower your idle setting. This will fix your HC readings.

Next, find out what the idle rpm limit is for the test. Run your idle speed up against the test limit speed, with some margin so you don't fail for exceeding the speed. If idle limit for the test is 1000 rpm and you're currently idling at 650, bump your idle speed up to the 850 range.

Finally, once the timing has been fixed and idle speed set, adjust idle mixture by setting both idle mixture screws equally and then turning them in (lean) until you get a 50 rpm drop in idle speed (this is called idle lean drop). Make note of where they were set before you start this, and then make note of where they end up with the 50 rpm lean drop. Verify that the 50 rpm lean drop setting is, in fact, leaner than where you started.

This will get you to pass. Shouldn't be any problem.

 

Thanks all - I'll let you know how it turns out.

 

It hasn't been suggested, but you might also consider dumping a bit of alcohol into the fuel. The oxygen in the alcohol will lean it out a touch and should help your CO situation.

 

All right - Thanks to all of your assistance - I passed.

I reset the timing to 10 initial, I am running a MSD HEI.

I backed the idle mix down until it caused a 25 rpm drop on each side, then re-adjusted the idle to about 925.

Here are today's results:

Loaded HC: 85 (was 104)
Loaded CO: 0.24 (was 1.17)
Idle HC: 214 (was 491 - fail)
Idle CO: 2.83 (was 7.85 - fail)

Once again they didn't physically look at anything on the car except the gas cap. So the AIR pump stays off for now.

Good to go for another year! Thanks Again!

 

Congrats

Always a load off your mind when you pass emissions.