Question1985 Chevy 2wd Silerado 305 engine w/4bbl carb 85,000 orignal miles.
Vehicle is idling rough with hesiation on acceleration and under load, black smoke from exhaust under acceleration, I know it's running rich from the black smoke and the smell of gas from the tailpipe. I could not locate any air/fuel adjustment screws on the carb. I have repaced or checked the following with no improvement:plug wires, plugs,cap,rotor,engine timing, carb floats, compression test all cylinders check 175-180 lbs.The problem started two days ago, any advise would be appreciated.I have owned the truck for 10 years this is the first time I have had a problem.
Thank You !
AnswerThe carburetors that were installed on vehicles in the last few years before fuel injection are extremely complex due to emission requirements.
If your choke is operating properly, you are probably looking at having to get the carb rebuilt or replaced. The idle mixture screws are sealed under steel caps that are pressed into the base of the carburetor. A special, mini-sized, hole saw is required to drill the caps out in order to make adjustments.
Installing a rebuilt carburetor, or even a new one, is probably going to cost less than trying to repair your old one.
