tuning the screw for idle rpm

My rpms gets as low as 400-500 during idling so you can feel the engine shaking every couple of seconds at a light. I see the screw to tune the idle rpm, but I can't find a tool that will fit in there. It's all cramped in there because the fuel injectors stick out too.

I asjusted the timing on the distributer and it's as good as it gets.

Know any place where I can get this tool? A standard socket wrench is too big. The small one is too big too.

It's probably not that your idle is too low, it is probably that your injectors are a little dirty or your plugs need to be changed.

Usually when my engine gets the little-shakies it's because there's a drain on the electric current (from turning on the heater, or lights, etc..), but my idle is right around 500 RPM.

I will check my plugs and I'll try fuel injector cleaner and see if it goes away.

i idle around 800, and theres also an occasional dip to 600 or so when sitting at a light for a long time