Pontiac Repair: car will not start, cam timing, chain tensioner

Question
g.m. 2.4 ohc will turn over and allmost run. scan gave code  for  map-- cooling fan-- tps changed still will not start and stay running,also sometimes when trying to start
it back fires out the throttle bodyacts like battery is dead when it turns slow sometimes,have new battery thanks

Answer
What year is this car? You question is a bit vauge.. It could be a bunch of things. The map sensor code could because it was running poorly. The fan code could be a whole bunch of things. Does this have a security lamp that comes on or is flashing? It could be a security system issue not allowing the engine to run by cutting the fuel off. The backfiring could be because it's running out of fuel or it could have an engine mechanical issue. This engine is known for the cam timing to jump it it has a lot of miles on it. Either the chain tensioner breaks or one of the guides for the chain breaks usually the one in between the 2 cams on the top. That is a last resort to look at the engine it's self. Does it sound funny when cranking it over? If so it could be out of time. Check the fuel pressure.. These are just a few on many things to check.. Good Luck :)