'83 with recently rebuilt 22R failed emissions with high CO. 70.4311 gpm and the limit is 65. The note on the form says that's usually due to the mixture being too rich. I figured I might as well change the plugs, cap, rotor, wires and air filter while I'm at it. The oil is new. Should I try the tune-up and have it tested before monkeying with the mixture? Is there anything special I should know about this engine/carb regarding emissions? I've never had a vehicle fail emissions so I'm new to this.

If the Plugs/Cap/Rotor/Ignition wires/Coil have a pile of miles on them, it wouldn't hurt to upgrade them (I used the stock NGK plugs BPR5EY I beleive they are, Accel 8.8MM Ignition Wires, MSD High Vibration coil and the OEM cap/rotor and startup/takeoff was alot nicer, and obvisouly much cleaner combustion. I don't know too much about these particular carb vehicles. depending on how many miles are on the truck your catalytic could be plugged up and possibly your mixture is off a little bit. Obviously try the cheapest route first, more then likely that will cure your problem

Since you are just failing, do the standard tune-up, also pull the cat and see how it looks, you should be able to see light through it. If the cat looks good, the tune-up might be all you need. Also make sure the engine is good and hot, if you live in town take it out onto teh highway for a few miles, and try to get the shop to check the truck when you get there, don't let it idle while you wait.

You can also try running a higher octane gas, mixing in a gallon of denatured alcohol to 10 gals of gas, a new cat will knock the numbers down(unless your cat is already new). These are the cheapest approaches. If none of them work, you will need to adjust the carb, though a 5 CO higher is doubtful that it is the carb.

Thanks for the replies. The plugs and wires were fairly new having been replaced in the last 1000 miles or so. I replaced the cap and rotor. They were fairly fouled. I seem to have a bit more power but could be just my imagination.

The truck had a very rough idle when it was warm/hot. I tried to adjust the idle and mixture. The idle can't even be adjusted. The screw to adjust it never touches the bracket to even move it. I wish I could find a valid schematic of the carb. I found a place that will sell me a rebuilt one for $250. They are Import Carb Rebuild in Denver. I'm sure the rubber diaphragms are all brittle and it wouldn't hurt me to get a new one.

BTW, the truck passed emissions seven months ago. I put some fuel cleaner in it and will see how that does.

Check the '85 FSM at the top of this section, all the carbs are pretty much identical, unless we're talking a 20R here, that should help ya.

That helped me identify parts. Thanks so much. I was adjusting the fast idle rather than the idle screw. That explains my first problem.

I've got a rough idle when the truck is hot. I have to imagine that if I can fix that my emissions test would be cake.

Im unsure of how these carbs are setup, but is the choke stuck on?

make sure the next time you take it in to get smogged its nice and hot and your timing is perfect

i will normally run mine for around 20 min just up and back on the freeway just to get that cat goin, its amazing the difference you will have in emissions
hope this helps <img src="/forums/images/graemlins/kewl.gif" alt="" />

And don't pay attention to the signs there that tell you to turn your heater on, because a colder engine gets better emissions!!! at least that's what the one by my house says <img src="/forums/images/graemlins/rolleyes.gif" alt="" />

No, if anything, it doesn't come on when the engine is cold.