Chuffing noise like a train

[Ollxee]

My car is chuffing (similar noise to when a human imitates a train). Anyway it seems to be in the intake manifold. There is an oil breather which attaches so does anyone recon it may be from that. I took it off from the airbox end and there is positive pressure and when I took it off it air was coming out like it’s supposed to. The chuffing noise seemed to get more distinctive due to it not being concealed anymore. So does any reckon it’s a sensor or a blocked breather tube?

[CitroJim]

Is the car running well?

Often, a distinct chuffing noise in the inlet manifold indicates a leaky inlet valve... Or, at best, a broken vacuum or breather hose attached to the manifold.

The oil breather you speak of is the PCV (Positive Crankcase Ventilation) valve and usually gives no trouble...

Check the chuffing noise is not originating from the sump by removing the oil filler cap and listening with the engine running. A distinct loud chuff, and possibly smoke, from here may indicate excess blow-by past a broken piston ring or worn piston/cylinder.

I'd recommend you check all pipes attached to the inlet manifold and then the valve clearances in case of a tight inlet valve and then, if all clearances are correct, a compression test on each cylinder.