I have a Q jet,17084280,R4-M4ME, 1984 Camaro Z-28, 5.0 L, 700R4, completely stock engine/carburetor internals and setup with the exception of EGR removal. Just a cruiser. I have used this setup for years and always lived with a minor off idle stumble. I decided to try to do something about it ,so I ordered a kit and Cliff's book. Everything went according to plan, the only mods being a new float, opening the idle screw mixture holes up as per recommendations because, it was said that these carbs ALWAYS run lean, and putting an Allen head screw for external adjustment of the APT , APT was 2 turns out stock.
Upon doing the tuning, everything was normal,vacuum19-20", steady needle, indicating engine internals are OK, starts good ,idles 750-800 RPM, idle screws at 2 turns out, electric choke still has the rivets in the adjuster from factory, but now I have a MAJOR stumble off idle when cold. When the engine warms, choke comes off as normal, the stumble is marginally better but still significant. If I try to 'push' the throttle through the stumble, it will do a variety of things..... puff back through the carb with quick advancement of the throttle, the engine actually quit running one time, but more times than not it will stumble, stumble, then pick up and run properly as you get moving. As the engine gets warmer , the stumble gets less pronounced but is definitely still there. when decelerating the engine lugs in the higher gear and then clears when the downshift occurs.
I am unsure if it is a lean or rich problem, but, am assuming it is a rich condition due to the fact that the only change is opening the idle air screw passages.
I have; adjusted the idle air screws to completely closed, adjusted the APT out to 3 turns, then adjusted the APT in to 1.5 turns without effect and thought long and hard. Also, the secondary air valves only start to crack open when the throttle is mashed and held open. I need some outside help, any suggestions for someone?
Thanks, for your consideration, Dale.
