Although I've tried to search for specifics, I am unable to figure out the search function. I am failing the emissions test in NC. HC PPM reading is 411 and should be 220 max. CO% is 5.55 and should be 1.2 max. Truck has new carb, plugs, wires, roter/cap, and PCV valve. Truck starts and runs fine. I haven't a clue where to start. If this has been addressed somewhere on this site, I am at a loss to find it. All my searches produce over 400 targets, most of which have nothing to do with my search parameters.

 

Has the carb been adjusted? Most new carbs come set rather rich if I recollect correctly.
How old is the Cat?

 

I recently bought the truck and didn't install the carb myself so not sure of mixture adjustment. However, I have verified idle speed, fast idle speed, timing etc. I just noticed that the vacumn to the air bypass valve has been capped off, which could be the problem. I'm thinking that the air pump isn't getting air to the cat. Cat appears to be original equip. As soon as I can figure out the proper vacumn hook-up to the air pump bypass valve and make sure it's hooked up properly, I'll get back to you. Thanks a lot for the response.

 

Got it fixed. Studied the vacuum diagram under the hood for 3 days and finally found a cracked vacuum line that was causing the cat to be COMPLETELY BYPASSED. Upon repair, the HC (ppm) went from 411 to 52 and the CO% from 5.55 to .21. And who said that cats don't reduce emissions???????????

 

Nice job, glad to hear you found the problem...

Couldn't of been that bad on a carbed model Gotta love em'.