I have been driving the Buick to work and back the last week and half. Its been running good and has been fun to use it as my daily driver. However, it has had an off idle hesitation since... well forever. It is only noticeable if you are cruising at say 30, let off the gas to coast and if you slowly ease into it (traffic). It is barely noticeable, I can almost hear it more than feel it. Would this be a possible accelerator pump adjustment? near stock 455 QJ rebuilt a few years back.
Could be...there have been a lot of complaints that the old rubber rebuild parts don't last long with the 10% ethanol coming out of the gas pumps these days. The big q-jet guys like Cliff Ruggles and Greg Gessler have ethanol safe parts to offer if that's indeed the issue. Devon
First order of business is to upgrade the internals with modern ethanol compatable parts, and a good cleaning. I recomend pulling the idle tubes as described in my book, as they get "varnished" up from years of drying up cycles, and there is no effective way to clean in and under them without pulling them from the casting. With this new fuel, it's pretty common to experience a very slight lean condtion at cruise. It is easily corrected. We've found that adding about 5-7 percent more fuel does the trick in most cases. On the early Buick carbs, we do this by installing an external APT screw in the baseplate, and raising the metering rods slightly. This increases part throttle fuel only. I keep seeing folks installing HUGE jets into the early Buick units to "cover" this problem. Going to larger jets changes the entire fuel curve, heavy part throttle, and at full throttle. Here is a pick of a modified throttle body with external APT screw.....Cliff
