Just replaced my pedals on a very old Norco MTB. I noticed while working on it that the whole peddle structure is wiggling from side to side is this normal ? I took the plastic caps off the base to see if it is an easy tightening fix, but not sure if tightening that bolt is the way to correct the problem ?
There could be a couple different issues at work, but it's most likely that the bearings need to be re-greased and/or tightened. On some pedals, that little screw simply holds the pedal body together and the amount of grease in the bearing area will determine how tight the whole assembly holds together.
On the other hand, some pedals have a preload that adjusts how tight the assembly is, simply tightening this might solve your problem.
I would recommend tightening that bolt and see if the problem persists, if not good; if it does, then either replace the pedals or take them in to a shop to take a quick look.