22r high CO Failed Emissions

[zatman2]

I have a 1990 pickup w/22r engine and high altitude carb and live at about 5400ft above sea level. Emissions failed with high CO. I replaced ignition wires, cap, rotor, coil, catalytic converter, smog pump, spark plugs as well as adding a rebuilt carb. Have also replaced timing chain, gears, tensioner etc. although not because of the emission issue. I locked the choke wide open, replaced the vacuum lines and temporarily pulled the air cleaner. I noticed that the butterfly next to the choke remain about half open with the engine hot at when operated throughout the rpm range. Engine has about 168k miles runs strong ,idles smooth. In the past it generated CO readings of 5.48 GPM and now it failed at 29.3 GPM. Need to get below 25 GPM. What have I overlooked??

[jetwhine]

zatman2,

I would think that you need to address the butterfly that is half open. When warm all butterfly's should be all the way open except for the throttle butterfly at the throat of the carb. With that butterfly open only partially at 5400 ft I would think that would be the problem with the high CO. There is also a high altitude valve on your air intake filter housing to help control you engine idle at altitude, you might want to make sure that is working also.

[Rh1n0_86OneTon]

Your EGR tube is clogged at the elbow where it feeds into the intake. It clogs with carbon and is like chipping coal to clean out. Two bolts at the elbow (different lengths so pay attention), two bolts and a nut at the EGR valve. You will need a new intake gasket to cut the part that goes underneath the EGR and the gasket for under the elbow and some dental picks.