Lately and before this problem occurs I have started hearing some noises when the rpm gets to 3k ~ 4k when accelerating on the first gear, my car is automatic but I hear that noise only when starting from 0 mph. Now, I flat the gas pedal but the rpm keeps increasing very very slowly and it won't get above 3k ~ 4k. A friend suggested that I use the manual gears (2-L, 3, 4) and try if this solves the problem but it's still the same, the car accelerates very slowly and the rpm won't go above 4k even when I flat the gas pedal. Yesterday I have tried and put the gear on N and revved the engine and it reached 7k and the response was normal.
There are several things in my head, it could be a gear problem since I hear a sharp and short whistle when the gear is shifted up, it might be a timing belt thing though since it is been too long since I replaced it. my Air filter pipe that connects the air filter to the engine got broken and I didn't notice it until the engine shut down on me while driving. It might be a catalyst problem but if it was then the engine shouldn't rev high when the gear is on N.
what are your thoughts?