You may need to put single quotes around the basis function selection:
-stim_times 1 stim.1d 'TENT(-2,14,8)' \
Are you trying to catch some BOLD response 2 seconds before each stimulus? Is your TR 2 seconds? In 'TENT(b,c,n)', you want n to be such a number that c-b is divisible by n-1, not n.
Also you probably don't need that many number of tent functions: The more basis functions, the higher cost of degrees of freedoem. How about 'TENT(-2,14,5)'?
Gang