VS Ute Knocking noise

[jwaye2]

My 97 VS V6 Ute has a knocking noise in Idle. once u apply any amount of throttle it stops knocking. also in 1st gear taking off runs very rough but second gear onwards runs great. Fuel system is all clean and working and so is ignition system. any ideas on what the problem may be?

 

[SP00KSTER]

is it a manual or auto?

 

[jwaye2]

is it a manual or auto?

Manual... sorry should have mentioned that

 

[SP00KSTER]

if it's a manual then you might need to change the oil in your gear box as it isn't uncommon to get gear chatter that sounds like a knock, also when in first gear then engine has to cope with a fair bit of force which will bring down the revs so id be looking at cleaning your plenum chamber if it hasn't been done for a while as it will increase more controlled air flow allowing the engine to run a bit smoother, also check your error codes see if anything comes up like a faulty sensor as this will affect the way the car runs. if you dont know how to check the codes here is a link
https://forums.justcommodores.com.au/threads/checking-error-codes-vr-vs-revised.22307
the pictures on the how to are near the bottom if you struggle with directions
Hope this helps in some way.

 

[jwaye2]

Cheers mate. I had a suspicion it might be gearbox related as there is a slow oil leak. ill have a look tonight and see how i go

 

[jwaye2]

gearbox seems to be fine. plenum is pretty clean. seems to me the sound is coming from the Harmonic Balancer. could a stuffed balencer be making them kind of sounds?

 

[moggy]

A stuffed balancer will make a knocking noise like the bottom is about to fall out your engine.

 

[jwaye2]

yer thats what it sounds like. freeks me out when i stop at the lights sitting in idle. might aswell replace the crank angle sensor at the same time.