My motor has a noise.
It is not constant, and happens at the cusp of power and engine braking.
It sounds like a diesel engine in a truck, a deep knocking, not a pinging or rattle noise.
If the car had the keys removed and was still running, you'd hear a similar noise.
When I get the revs too low in the old diesel truck it makes a similar noise.
It is not there at constant revs, and not audible from the cabin, but very audible in the engine bay.
It is quite dificult to make it sit on the noise, as it seems to be at the transition from load to engine braking
Unplugging injector/spark on each cylinder does not make it go away, and the roughness makes it mildly worse.
If I had to punt on which end of the motor, I'd say the flywheel end, but I'm not totaly certain of that, as its a broad sounding noise, not specific to an area.
I took the valve cover off and that didn't really narrow it down either, but it does not appear to be the head.
The motor is running very rich acording to the O2 sensor read out.
Does any one have any idea what this might be, or any other tests I can do to confirm or eliminate any of the usual suspects.