1985 Chevrolet El Camino throttle backfire

throttle backfire when you press on the gas no matter if cold or hot

Bad accelerator pump in the carburetor is likely. It my also be a worn timing change but I’d bet on the carb first. It needs a re-build. Also look for vacuum leaks. If the vacuum hoses have never been replaced, do them all, now. Same for all the plastic vacuum tees as they will ALL break when you replace the vacuum hoses!