I came back from prop testing Sunday evening, it was calm when i took off but the wind had picked up and was a good cross wind. As can happen, everything is ok until the tail comes down, then the cross wind tuns one into the wind and across the runway, no problem getting stopped before edge of runway but at that point either need to shut down, straighten it up and taxi some more or drive across the infield, in this dry ground, and continue on the taxi way. This is what i did and hit a rough spot, some little bumps, not bad but one of the ignition boots came off on a plug, the engine continued to run on one cylinder but no power and did not want to accelerate above and idle. Upon checking the situation the little screw on terminal on plug, which i had tightened normally when installing new plugs about 23 hours ago had come undone, even though it was in a spring load clip on type terminal and the boot had been worked loose.the little screw end of spark plug was still in the terminal, inside the boot. I am going to lock-tite that little critter now.