Ticking/Tapping noise under low rpm load

[spatch]

Driving along the other day with the window down and as I overtook a cyclist I noticed a ticking(tapping) noise under acceleration.

I tested it further and I have found that if I accelerate from about 1000rpm with my foot fairly well down on the pedal, there is a ticking/tapping until the turbo begins to spin up - about 1500rpm. If I do not load up the pedal too much it does not do it. If I put my foot down hard with the revs slightly higher (say 1500rpm) it does not do it.

Doesnt seem to make a difference if hot or cold.

Lastly, the noise speeds up with the engine and the frequency seems to tie in with the engine speed (but RPM/2). What I mean here is that the noise seems to occur every time a cyclider would go through an action eg a power stroke or exhaust stroke or fuel injection.

Any ideas?

Cheers,
Mark

[Gsi3.2]

it's just diesel knock...not an issue if it goes away when the tubo boosts and it's only happening under low RPm load..

[Stevel]

Have you checked for a cyclist under the car.

[spatch]

it's just diesel knock...not an issue if it goes away when the tubo boosts and it's only happening under low RPm load..

Thanks, possible I suppose, but why do I only seem to get the noise from a single cyclinder (perhaps I did not make that very clear). The frequency of the noise corresponds with just one cyclinder making it, not all six. If it was diesel knock would I not get it from all six??

Cheers,

[spatch]

Have you checked for a cyclist under the car.

Thats definately not the cause, she is in the airbox. That reminds me, I must clean the air filter soon.