If you downloaded a car that has els in the title somewhere inside it's folder should be a file in your case if the car was intended to replace POLICE3 your will see a els file for the corresponding car. Better yet send a link to the car you have installed. I can look it over. Also if you have els installed already there should be a police els file under ELS>Pack_Default. You can simply duplicate it and rename it to police 3. Some cars require custom meta and carcol files to function properly so if the car you are using requires that then that could be your problem.