I wrote a simple program to calculate pi using Leibniz's formula on my TI84+SE, but, though it can do the 4.6 million iterations required to make it to 9 digits, it gets truncated. Anyway to fix it?

Without code it's impossible to say Yes. Are you storing to Ans? A variable? a List? I haven't saved such a long decimal - or number - to a variable in a long time so it could be the OS rounding the number. Try saving to a List or a string or just putting the result on the graph screen for each iteration. When the graph screen fills up pause and wait for the user to down and continue along at the next step. If you want to go farther, include a step counter so you can include a previous option! Maybe alter the variable used in a For() loop.