I have a 2002 Mitsubishi Eclipse GT...it has been overheating lately, then today when I went to leave work it started right up, I was able to rev it a few times but it idled down and when put in gear it died seconds later. Sputtering noise coming from tailpipe, all fluid levels are where they should be...what could be causing this problem? someone advised me that it may be my fuel injection, water in my gas tank or bad gas?? please help

problem fixed for now...filled tank up with premium & put fuel injector cleaner in...started right up and ran...still idles a little low but ill figure that out later

Keep running injector cleaner for the next two fill-ups just to be sure.
Also look into cleaning out the engine with seafoam.
If you decide to do that I'll explain how.