There's a distinct possibility I might be headed back to Colorado in the next few months. My '78 is originally from Denver, but it was not sold with the high altitude package. I have the original manifolds and it wasn't equipped with an air pump. It is currently cat free..

My question is about the emissions piece. I know there are several ways to "cheat" the test" as far as making sure it's warmed up, oil is fresh, and lean it out if necessary.

Can someone give me a rundown of the tests? I have seen conflicting reports... but from what I can tell is they do a visual inspection for cats.. do they check EGR? What about the actual sniffer test. Do they just check idle? Or do they check it at speed, too?


Thanks,
Eric

 

They will look for a cat (I was told by one tec that if it came with one cat it has to have only one cat, and told by another that as long as it has cats on both sides duels are fine even if it didn't come that way) and look for an emissions diagram under the hood. You must visually have what the diagram shows. If there is no diagram it will depend on the tec you get and the mood they are in. Just my experience. That was 6 months ago when I was looking at a 1981 vette, if you have 1975 or older you can get collector plates and no emissions test will ever be required. They actually put your car on a dyno and run it for about 5 minutes.

 

Denver and the surrounding Metro Area is on what is called the "Enhanced Test." Here is the basic rundown:

Cars 1975 and older do not have to be emissions tested. 1976-1980 cars can be tested at either a "Colorado Air" facility or at an independent shop. There are very few of these independents left, but these independent shops only run the car at idle and at no-load elevated rpm. The Colorado Air facilities will run the car on a dyno on a simulated road test.

The car must pass visual and tailpipe emissions at either facility: The car has to have the cat on it, and it has to have an EGR, if originally equipped. I've never had an issue with headers on a car, but the cat(s) gotta' be there. They don't verify that any of this stuff is actually working, as long as it appears to be in place and appears to be hooked up... Keep in mind that real mechanics at the independent shops are actually a heckuva' lot smarter and experienced than the knucklehead kids they have running the Colorado Air shops, so it's easier to get by with stuff that's not hooked up at the dyno facilities...

The acceptance criteria for the pre-80 cars is pretty loose. If you retard the timing back to factory spec, run ported vacuum to the vacuum advance, and adjust idle mixture to obtain a 50 rpm lean drop, and then elevate your idle rpm up to around 900, you will pass with flying colors.

Lars