lindsey 80 tow behind

i have a lindey 80 gas tow behind air compressor when i start it it run but when i pull the lever to billed up air pressure the idle is sapose to kick up then stop when meets the right psi when i pull the lever the idle drops real low and will bild up pressure but when u use air the compressor rpms will no rise to keep up please call me and help 617 678 6573 ncarbone, NEWTON MASS USA