Hi all I have an 84 gs all stock and it has a problem with the carburetion. When I am braking for a stop sign or light and I have the clutch in my engine hangs at a high idle 1800-1500 rpm, then slowly settles down to 800 rpm. If I load the engine via the clutch with the car stopped the idle comes down immediately and stays there. I have adjusted the fuel screw and I can make this better or worse, but can not eliminate it. This car just passed CA smog 1 month ago, and I when it did the fuel screw setting was such that the idle hang was very long lasting. With constant tinkering with the fuel screw and idle adjust I have minimized it the best I can. Also in the last 3 days I have noticed that when warming up with the choke on I have a miss that feels just like a bad plug, but the engine runs fine with the choke off. Does the choke circuit bleed fuel or block air to just one rotor or both? My idle has not changed so I assume I am getting the right amount of fuel from the low speed circuit. Also I checked the shutter valve the way mazdatrix says and it seems to be working correctly, and there are no abnormal sounds.

Help if you can

 

Does qiuckly tapping the throttle one or twice with the clutch pressed in make it settle? If so your return spring could be getting tired or something is binding a bit. Could be your throttle cable is getting a bit rusty and getting hung up.

 

Thanks for the response. I checked and the throttle is working properly. It really acts like the fuel screw is too rich but I am fairly certain it isnt. I think I need to rebuild the carb. It acts like the low speed circuit may be a little dirty and I have the fuel screw open a litttle to far to compensate.