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VS Commodore V6 noise & hesistation, PCV valve???

terry_toughnuts

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Hi everyone

I know this is going to be a little vague but I want to get some advice on a noise I'm getting in my car.

Basically the noise is sort of between pinging and lifter tapping but I'm fairly sure it is neither. (I’m just using that to try to explain the sound)

The noise comes in at 3/4 to full throttle under load and does get faster with revs but isn't dependant on engine speed. (i.e it can do it in 5th at full throttle doing 100 or 3rd full throttle doing 100) It won’t happen every time I hit the throttle but it seems to be coming more and more consistently. The thing is I can’t get the noise when I’m parked because I can’t get the motor under enough load when in neutral.

I've also have problems when its cold, the motor is very hesitant and wants to stall when the throttle is dabbed. Don't know if it’s related or not. I've stuck my head under the bonnet to see if there is an air leak, it does sound like there maybe air getting in somewhere, but have checked everywhere and can't find anything. It also has a K&N filter so the intake is quite loud.

I've checked the engine vent hoses on the throttle body and back to where they go and have renewed them so not that and I've also changed the gasket on the plenum cover thinking that air might have been coming though there. (Not that it would cause the noise but it could explain the hesitation when cold)

I'm starting to lean towards the PCV valve being faulty; would they make noise if they aren't working correctly and would they cause extra air to get into the air/fuel mix making the car run lean?

The mods on this car are only a Holden S/C cold air intake, K&N Filter, 1.9 yella terra lifters and a chip from green foam. Unfortunately the noise and hesitation have come in on there own, I don’t particularly remember doing anything that’s brought it on.

Anyone have any ideas????
 

ephect

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just making sure, u own a VS and a Foamy chip? coz i didnt think Foams did VS's! if he does he's been holding out on me.

i have the same mods bar chip, and had the same problems with hesitation, until i earthed my oxygen sensors and replaced em.

but you have a ticking sound that follows the engine revs. sounds like you've done some testing, hows the oil looking? to me it either sounds like piston slap, sticky lifter, or oil pump on its way out not supplying enough oil to the top end. possibly run some oil flush through the block

did it log any codes?
 

terry_toughnuts

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I've replaced the O2 sensors about 3 months ago but didn't do the earthing trick that is floating around on here. I guess that’s something to look into.

I've checked for codes, its not logging any codes at all.

Oil is about 2000kms old and has been checked for level as is still ok.

I was thinking lifter at first but I remember when I installed the lifters what they sounded like with no oil (before they were lubricated with engine oil) when I first started the motor and its not the same sound.

Piston slap??? I hope not, I don't think I've ever actually heard piston slap but you would think it would be more consistent if there was something that majorly wrong.

Can anyone tell me when the PCV valve actually vents open? Like when does the ECU tell it to vent? Full throttle??

The car has only had a full 2.5 exhaust and extractors fitted about 3 months ago if that helps at all.

And yeah it is a foamy chip. Jason I think only changes the timing to run premium unleaded. (Which of course I have been)
 

Boonz

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the pcv is controlled by crankcase pressure and manifold vacuum, it vents back into the manifold because it is mainly exhaust gasses, which is why its not allowed to vent into the atmosphere before the cat converter
 

Gassed VT

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Hi,
Just been reading your thread and sounds like the same symptoms my car has. Did you ever work out what the problem was?
 
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