I was in stop and go traffic, the weather was hot and I had my air on. When I was able to accerlerate, the car sounded funny and felt like it was slowing down. I tried accerlerating but I could hear the car as if it was gunning the car but it still felt like it was slowing down. I pulled to the side and had the car towed homw. I started it at home to park it and it didn't make that high ideling sound. What could be the cause before I bring it into the mechanic? Thanks