As Christmas draws closer and I am rushing to get all of my wife's presents finished, her Fuji Allegro (one of her presents) is shifting on it's own. When you make it shift, it shifts fine, then it shifts back to either the middle gear or all the way down to the little gear. Adjusting d/r s is a new thing for me, so please bear w/ me. Thanks for the help

It could be a couple of different things but it sounds like the cable is stuck some place and while you are applying force (shift) it moves and shifts and when you move your hand from the shifter it tends to return back and reshifts to the original gear. I'd change the cable and the housing first (could be catching in some part of the housing that is torn apart on the inside). If that does not work, I will check the springs in the shifter. I assume that you have problem with only the rear or only the front and you are using friction shifting. If that does not work, then you'd need to adjust the RD or FD

It sounds to me like your shifters are slipping, thus allowing the rear derailleur to downshift as the shift levers slowly slip. Correct this by taking one shift lever apart at a time, clean it thoroughly and put it together. Once assembled with your cable fitted and attached to the rear derailleur, ensure that the friction adjustment(the little screw in the middle or each shifter) is tightened up enough to create sufficient friction to prevent further slippage. Hope that is a help.

When I picked up the bike, I really had to muscle the rear lever to make it shift. I loosened the tension screw? and now it shifts easier but now it shifts itself. I pulled the cables out of the housings and lubed them (seemed smooth). I'll clean up the shifter guts (it is friction shift) and see if that helps. If not then I have some other shifters floating around (suntour ratcheting) and see if that'll work. Btw, the original setup on the Fuji is suntour AR.

A new cable costs about $1. Don't mess around with the old stuff. Buy a replacement cable kit at Walmart for $5, and replace them all: brakes and both shifters. Its an easy job. Then make sure you have enough tension on the retention bolt holding on the lever, so that it does not slip on its own.

You may want to replace the cable housing, as well.