Starter sputters then will catch

Windstar 2002 starter sputters then will start usually....put fuel injection cleaner in gas tank, mechanics put a new filter on valve...now it hesitates from like 40 mph then goes. Same mechanics put a fuel line in a few months ago. The "low tire" light comes on and stays on most of the time...not sure if this has anything to do with anything. Things are very tight right now financially.