20v knocking

[spoon]

my 20v has started knocking a bit at high revs (over 7000) under full throttle - anyone know why? im using 98octane fuel... is it just cos its too advanced or is there something more as i checked timing about 2 weeks ago and it was fine - ill have to check again tho.

[Robert]

How many kms has the engine done?

[slide86]

knocking or pinging?

a knock could be internal engine noise....ie bottom end.

[The Witzl]

4age's are good with knocking.... rebuild the engine

[Ben Wilson]

Try pulling a bit of timing out and see if it still does it.

If not, it could be a crack in the exhaust manifold or something more sinister/expensive...

[adamaw11]

I'm wondering how you could even hear pinging at that rpm. They do make a fair bit of noise when your up there at wot.

Are you getting some sort of indication from a knock sensor? using factory computer?

[Selk]

is the oil low ?

[spoon]

the car has been using oil, dont know why - um noise is like a vibration sound - cant be good! but only at high revs. hopefully it wont require a rebuild - not yet anyhow - i only pretty much put it in! maybe 1500km ago! before that it was import engine - not used here... also auto so i cant imagine it wouldve had a hard life. Im using factory computer (manual one). Is there any sort of oil i should be using in this engine? ATM im using mineral based 10w40, as ive heard they dont like the synthetic stuff. maybe this could make a difference?

[adamaw11]

Pinging is not usually described as a vibration sound afaik.
If its some kind of loud vibration that just kicks in over 7k, then yeah maybe it could be something bad.

Check if anythings loose or rattly around the engine, cause something might be resonating at a certain frequency. You can get some pretty strange sounds sometimes from harmless metal things resonating.

Using factory computer are you? it turns the vvt OFF somewhere around that rpm, wonder if that could have anything to do with it. Sometimes I've noticed a bit of a buzzing sound when vvt comes on at certain rpm but think nothing of it really. Maybe try unplugging the vvt solenoid and see what difference you notice in the sound.

If it still goes hard, just keep driving it, make sure the oil is always topped up and keep enjoying it.

[spoon]

ill give the vvt a go - otherwise yeah, il just thrash it more! be surprised how many things are fixed by a good thrash! thanks fellas

[Ben Wilson]

Pinging is not usually described as a vibration sound afaik.

A friend of mine described what he thought was the sound of a loose exhuast heat sheild in his AE86 rally car for a while before he melted a piston...

[Mr Revhead]

internet diagnostics is hard!

checked ya engine mounts?

[spoon]

hmm today i had a look at my speedo sender unit as my speedo wasnt/isnt working - pulled it out of the gearbox and the liquid that followed leads me to believe that the gearbox is the culprit. the gearbox has been on its way out (bit of whining and bad syncros) for a while, just didnt think it would be related. but my mechanic mate bets his life (big call) that the noise is definately the gearbox, so im gonna change it over the weekend if i can and see how that goes!