1989 chevy G20 sportvan.. 5.7 .. just bought as a project.. wont idle. new cap, rotor, plugs.. i notice that when i spray carb cleaner on the lower half of throttle body it will idle, stop spraying and it shudders and dies.. giving it gas does not help... 195,00 miles

 

I'd say time to overhaul the carb.

 

what is there to repairs??? I also replaced the injectors, rebuilt the fuel regulator and replaced the upper half gaskets... you do realize this is a TBI and not a carb??

 

sorry I misread

 

Take it apart, and clean it

 

I haven't looked at any of these specifically, but it seems you have a vacuum leak allowing air at the base of the throttle body. Maybe at close to 30 years old, it is time to replace the base gasket or rebush the pivot points.for the throttle plate.