car cranks but wont start sounds like it wants to catch but is popping and shooting gas back out of intake...wat would cause that...how can i find out if timing chain has gone out...and will a sensor cause this to happen...wat about my computer needs to be flashed by dealership someone help im stuck!!1

 

Which engine do you have? Sounds like it might be a broken timing belt.

 

2.5....the car was running fine battery was no good so i put a new battery in it...also i change the ecm because car wasnt getting spark or fuel n once i put the computer in it start getting spark and gas...would a bad crank sensor cause this

 

It could, or not. Any codes?

 

i tried using the old way by turing the key on off on off on and got a reading that way..how would i kno if timing belt is needed

 

Chances are, that if you have spark and fuel, you have a functional timing belt, as the spark comes from the distributor which runs off the camshaft. You could run a compression test. If you've got compression, then the camshaft is connected to the crankshaft and the belt is working.
They don't make it easy to look at the belt.
You said you got a reading with the key, what was it?

 

12 24 55

 

12 is nothing. Just says you recently disconnected the battery, but you put in a new battery so that explains that.

24 Throttle position sensor voltage low or high. Better check your TPS.

55 Just says that this is the end of the codes.

Only real one is that throttle position sensor code. Look into that.

 

wat is the tps?

 

throttle position sensor? will that cause it to run and cut off