To clean the Gross car carpet, fill a bucket or spray bottle with the detergent solution and soak the area you want to clean for about 15 minutes. This will help loosen dirt, shampoo, or suds built over time. Once the place is cleaner, rinse it well with water. To clean the heavily soiled car carpet, mix dish soap and water in a spray bottle and spray it onto the carpet. Allow the carpet to sit for a few minutes before rinsing off the soap residue.