My new dishwasher is properly installed and I recently had the sewer gas vent checked. I too had an awful smell in my dishwasher and although I only run the washer every 2nd day or so, I've never had this problem before. In addition to the smell, or maybe the cause, I found weird mold stuff growing down in the filter. I cleaned it periodically with boiling hot water, tide detergent and an oxyclean type bleach alternative (sodium carbonate peroxide) which did a good job of cleaning and removing grease, but the smell would return days later. Finally after much research, I came across some information about copper which I found interesting. Apparently, copper kills fungus, mold, and bacteria. It's suggested that by putting discs cut from copper plumbing pipe in the washer and running vinegar twice a month, it will eliminate mold, and bacteria that may be growing in the dishwasher. Apparently the copper leaches out of the pipe, and kills unwanted organisms. Sounded strange, but I know roofers use copper infused roof tiles to prevent organisms from growing on roofs. I put some discs of copper pipe in my dishwasher and leave them there (they're too big to get down the drain). I run vinegar twice a month and I finally have NO bad smells. It's suggested that using copper plumbing pipe will insure a clean metal, not a copper that may be alloyed with some other toxic metal. Pennies won't work. I know this may sound odd, but google what copper will kill, and you'll see why this works!