Battery Cable problems of the 2006 Chevrolet Trailblazer

We have had two 2006 Trailblazers and both of them have been nothing but problems for us. The first one we brought we owned it for six months and we had it in the shop six times (broken sway bar, heater two times, windshield wiper fluid holder two times, shaky front wheel and motor misfiring. We traded in hopefully to avoid more problems and went ahead after assurance that this one must just be bad and got another 2006 Trailblazer. This one we have only had for 2 months and we're already having problems. Three days after we bought it had to go to the shop for the radio not working properly. Then the engine starting misfiring and the engine light was on and it was running really rough. The tech thought that it was happening because the gas cap wasn't all the way tightened. (when the engine light comes on you loose power and I pulled out in front of a car on the highway and barley moved that's how I found that out. ) when he called me back he said that I had two cracked sparks plugs and the battery cable was loose making it start slowly. That was fixed but then 5-27-07 the engine light came on again and it was running rough just like before. It seems like everytime that the engine gets wet that it makes it misfire. I told the dealership this several times now. It had been raining that day. Everytime I take it in for the engine they tell me there is a lot of moisture under the hood on the motor. It's in the shop right now.