I have 3 pedal, and they all work fine with Expression . First off, use a good pedal, Ernie Ball is good-I have 3, and one is "weird" (I got it from the guy who designed it, Mr Ron Saul of Ernie, who ha a plant in San Luis Obispo. One pedal "may" have a 50K pot, and it acts hinky, I just subbed it for the other Ernie pedal. I refuse to have 3 pedal and 3 stomp, there is never enuff Real Estate, so it works out fine.
So anyway, measure the resistance on you Pedal. That's a start.
