width:auto not working

Page is http://newdrim.wpengine.com/product-category/electric-ranges/cooktops-electric/ and the image width is not scaling and the image height width ratio is wrong and messes up the picture. I’ve tried:

.category-products .h-product img, .section-single-product .h-product img { width:auto !important;}

and it doesnt work, but the selector seems to be correct because .category-products .h-product img, .section-single-product .h-product img { width:100px !important;} DOES make the image 100px wide. What CSS can I do to get the image to show completly but keep the height width ratio correct so the image is not distorted