HI i have a 1985 4x4 carb 22r that is running bad at low rpm. it sounds like its miss firing almost. but at high rpms and freeway speeds it runs like norm. i checking the timming i have it at 2* advanced or so. it all of a sudden started running like this. however on occasions it runs fine. i replaced the o2 sensor about 7 months ago and the pcv about a week ago. any help would be great

also replaced plugs, cap, rotor, wires. i have a spare carb thinking about swapping them and trying it out.

I did a quick search on your engine, and it looks like the timing should be at 8 degrees BTDC. I'm not 100% sure, but it couldn't hurt to try it. You can also try adjusting the air/fuel mixture, and add some fuel system cleaner. Good Luck!

Maybe it's the AAP (Auxiliary Acceleration Pump). If the diaphragm is wirn out, some gasoline is aspirated in the vacuum lines. The AAP is on he right side(side of fuel pump) of carburator, in the front. It's a 3 screw housing, about 1inch diameter.

To check it, start your truck , and clamp the vaccum line. It the truck starts to run great, change it!

(it's hapened to me last year)