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.