2001 Jeep Cherokee low idle when its cold

Since the start of winter when I start my Jeep it runs at an extremely low idle and will shut off due to it. I have to drop the auto trans from drive to 2 or 1 when driving thru my neighborhood to keep it running until it is nice and hot and even then sometimes it will drop down to low idles at a stop light usually down to 300-400 rpms. I run 92 octane and have put fuel injector cleaner in it. I can't see the spark plugs to change them since I havent found a manual yet. I think the plugs are inside the heads.