Checked the timing!

I have a 95 4runner 3 litre 4x4 automatic with 107k. the check engine light has been on for a while. runs pretty good, mileage isn't as good as it should be and sounds a little rough when idling. had the code read and says system is rich. i checked the timing and it was a little off, was 15 degrees and should be ten at idle. i set it at ten but didn't help the idle problem. i am just wondering what i should check next, coolant sensor, oxygen sensors or maybe something else. Any advice is greatly appreciated1 Thanks.