i have been working on an 85 pick up for a while now. it idles harsh and puffs black smoke. carb is re built, new fuel pump, egr valve, fuel filter, cleaned plugs and cap, running lucas fuel system cleaner through it. i can get it to run perfect for a day then harsh idle and smoke again. 160k miles and passed emissions. 2 bbl 22r engine. manual trans. let me know please.

 

you might try checking the choke to see if it might be sticking or the linkage could be binding up. the float level might also be to high or sticking.

 

With a rebuild on the carb I'm going to assume that there isn't a bunch of crud on the backside of the carb gumming things up. Have you checked the timing and the valve lash? Also, depending on the condition of the valves, you might want to consider running some sea-foam through the carb to clean the valves. When you say that it starts running harsh is it the next day when you start it? Or is it during the day while driving that it acts up again? It's a long shot but I've seen the vacuum advance on the distributor start sticking and not want to return properly. What is it that you do to make it run perfect?

 

honestly i dump a ton of carb cleaner in it and start it. once the white smoke dissipates it runs like a champ.it starts to act up within a matter of 6 hrs. after it cools i go to see that it runs correctly at all temps and i get the harsh idle and smoke.

thank you guys for helping me out i really appreciate it.

 

i have checked and double checked the timing . im fixing it for a friend so no valve lash checking yet. i am attempting to stay relatively in expensive.

 

It sounds like something is sticking, either the carb or something in the valve train. How much gas is left with the lucas oil cleaner in it? have you looked down the carb to look for excessive deposits? If the lucas is almost through the tank I would run seafoam through it. start the truck pull the vacuum line off the brake booster and pour half a can into the hose, if the engine doesn't die, shut it down, and let it sit for 10- 12 minutes. After letting it soak in it's time to play spyhunter, go out and drive the thing all the way through the rpm range, it will smoke like crazy, but will clean out any deposits in the carb, intake, valves, cylinders, etc.
Also IMHO the timing should be running about 12 degrees advanced.

If none of this works, check the compression, and the valve lash. Both are inexpensive and tell you a lot about what's going on internally. Plus while the valve cover is off for the valve lash you can look at the timing set. if the guide is missing from the driver side it's timing chain time.