engine noise past about 2500rpm

[alex2_s]

my (non - thrashed, 150 000 kms) engine has developed a knocking noise past about 2.5 - 3 thousand rpm... its very hard to drive sedately to make it change gears soon enough to avoid the noise and it makes it too when first starting cold (because of the high rev after starting) for a second... also makes the noise when warm and in neutral and raising the revs to that level too...
what could it be? Rod knock or something?

it seems to have lost power too, but i could be wrong. the temperature gauge is stuck at cold too, seems to have happened at the same time the noise started... related at all?

oil level is fine, spark plugs show a 'bit' of white on the electrode... ... i took the belt off and started it up it still makes that noise.

[alex2_s]

any thoughts at all???

[hako]

Do a fault code check Checking error codes VR/VS (Revised)

Sounds like its starving for oil at higher revs but if the oil light is not coming on then you'd imagine oil pressure is OK. Maybe post a pix of the plug.....maybe dropped a valve or a lifter is stuck but that would be evident at lower revs as well.

Could be a failing harmonic balancer - taking the fanbelt off does not always silence them,,,,see if its cracked or has a wobble.
Good Luck.

[alex2_s]

Yeah no error codes at all. That's what confused me, there's no 'knocking' noise at lower rpms. Harmonic balancer is a possibility, it still looks visibly fine and won't move by hand with the engine off and the belt isn't 'loose', but looking from a top view it does seem to have a slight wobble with the engine idling?? Also doesn't a failing H/B usually make a noise at idle etc.

Thanks mate.

[hako]

The noise you may get from a buggered HB can sound like "anything" - they all fail differently although the end result is the same - a dead stop! Use a mirror and check the rubber part of the HB....any split/crack is a sign.

[alex2_s]

unfortunately the whole bottom end is buggered according to several mechanics opinions, saying its better to maybe drop a new (2nd hand) ecotec in rather than fix it depending on damage...

[hako]

unfortunately the whole bottom end is buggered according to several mechanics opinions, saying its better to maybe drop a new (2nd hand) ecotec in rather than fix it depending on damage...

That's bad luck. Seems a bit strange for a 150k non-thrashed motor. Usually if the bottom end is shot the oil pressure light will come on. You can short out plugs to confirm....do a GOOGLE on 'bad main bearing/conrod' and you should find some info on making double sure although mechanics are rarely wrong.