I have a 1974 ford f100 custom, I have done almost all the work on it myself. Less the stuff you need a machine to do. It needs a tune-up but I don't want to take it to a shop and pay 200-400 to get this done. What is done on a tune-up for a truck this old? Would a tune up stop my idoling problem? it seems that after it is started it revs on its own and fluxuates between 500 rpm's and 700 rpm's?