Need Help WH Caprice

[Niper]

Hello I have a 2001 5.7 a4 wh caprice 200,000km it was running well and every thing was ok then i noticed that it did not respond to the acceleration pedal like it used to but i ignored it than after two weeks it got very slow and i would push the acceleration half the way for it to move but it was very slow and there was a firing sound coming from the front of the car i bought new spark plugs but nothing changed

Can someone please help me with this problem can it be the timing or the car computer
is it not getting enough fuel or air i am really confused

[SSbeast]

"firing sound" i'm unsure what the means is that like a bang sound like a gun sound? I'd be checking Fuel, Spark, and check what's coming out the exhaust. Are u losing coolent? Is the check engine light on? To have progressive loss of power something is dying or died. Also is there a mis-fire or does it back fire? Check the spark plug leads arn't loose or u haven't dropped a coil.

[Niper]

it backfires the sound comes from the engine not from the exhaust the check engine light is not on but the power train electricity light comes on sometimes but when i turn the car off and on it goes away and my cooling system is a fine and my engine oil is fine i am really confused

all the sparks are firing the engine idles fine but when i move and step on the acceleration a bit it doesn't move and it backfires i have to release the acceleration for it to move

[Niper]

i also noticed that when i turn the engine fells like i will turn off and the lights go weak