[77newell]

The pedal controls the air pressure sent to the spring loaded air cylinder on the engine that moves the throttle lever on the governor.

There are three places things can go wrong; pedal movement not changing air pressure, the air cylinder not proportionately moving according to air pressue, or the governor not proportionally changing engine speed according to changes in throttle lever position. The first two are the most probable.

I would start by putting a pressure gauge in the air line to the cylinder, then watch the pressue as you move the pedal. If pressure changes appropriately, then I would watch the cylinder rod movement as pressure changes. These tests will make the part causing the problem show itself.