my motor's had a dodgy rattle since it was first driven.after a good thrash coming back to tickover it makes an almost embarrassing rattle for afew seconds.i'm told by the nissan guru's its a sprocket for the vvt and they nearly all do it,probably did it when it was a tintop but i just never noticed and dont worry,its not worth the time and money to change it.
Whether its paranoia,related or unrelated reving it in a small garage i can hear another rattly almost faint knocking noise thats putting me off taxing the thing if its likely to be something else and a rebuild job.when do bigends knock?under load or on tickover?or cams rattle for that matter.its almost silent at constant revs,just injectors ticking and exhaust noise? Like said it might just be me panicing over nothing,i hope...
Chris

Have you got an sr20det? If so there are loads of things that rattle without being a problem - like for instance the tappets if the engine is ever inverted or tipped will chatter, what you should be worried about is knocking and squeeking! Squeeking is heard just before the crank pulley delaminates (which is surprisingly common on these engines!)

yeah,its a sr20det.cant decide if its a knocking or a rattle!only does it when building revs fast,which only lasts a second or 2,and cant drive it to see if it does it under load!when do things knock more,like the early signs?underload or on tickover?
only experience i've had with knocking is when a mates 6pot supra dumped its oil on the motorway and by the time he'd stopped it was totally shot and knocked all the time!

First things first work out where the noise is coming from - if you have a long ratchet bar you can use it in a stethoscope type way so get someone to play with the throttle while you push it agianst a few places in the block and head.

Its going to be a lot easier to diagnose when you know where the sound is coming from. AFAIK it wouldn't matter what the engine speed was as to the rattle/knock if it was big end/main bearings, only that at higher rpm other engine noises would drown it out so you wouldn't hear it.

ETA: The only other thing I can think is that if you have a fair bit of play in the turbine shaft (T28 turbo?) its possible that at high boost your turbo is hitting the fins on the compt/turb wheel against the housing - if it is that though I wouldn't expect your turbo to last very long!

[Edited on 15/5/10 by tomprescott]