Recently my car started to stumble, sort of like a miss when I'm running my A/C. It doesn't do it continously, but enough to aggravate me. The A/C blows really cold and a check of my freon was good. I thought it might have been low and the compressor was cycling on and off, but I don't think that's what's happening. I doesn't do it when the A/C's off. Anybody have an idea what might be going on here?