I just got this car (2001 Corolla CE) a few months ago and I started to notice that there is a low tapping/growling noise coming from the engine in 2, 3, 4 & 5 gears.
It has about 125000k on it.

It is noticable when the clutch petal is not pressed and has engaged the engine.
It is more noticable when I am accellerating than if I am not pressing on the gas, but always there, even if it is very quiet.

Is this a common sound for these cars?
Could it be the valves - it sounds like the noise is too dull for that though?
Could it be the Tranny? it is a standard.

The oil is up, but it is due for an oil & filter change soon.
I changed the oil & filter but not really any change.

Thanks,
Bill.