worrieing sound

[stevetubbyturbo]

i was working on my 2.4 td surf today (just fitting a reversing camera) i started the engine and let it get warm and took if for a drive down the road as its been sitting for a while and all was fine just driving onto my drive and gave it little blip on the throttle and there was a sound like a very loud diesel knock then the engine ran a bit lumpy.

i switch off the engine then tried to start it and it started fine and left it running after 5 mins took it down the road again for about 10 miles and up to 65 mph and its running fine and its not made the noise again.

as the car has been sitting for a while like 5 months im wondering if it may have collected a bit of water in the fuel.

any thoughts would be welcomed

Cheers

Steve

[BUSHWHACKER]

Maybe sludge in the oil where it's been dormant for so long, and strainer on the oil pick up pipe has become restricted in the sump?
I would change the oil anyway.