R34 Gtt Over Boost

[RBrennan25]

Hey guys,

On the drive home from Bathurst to Sydney I noticed the car was over its normal vaccum at idle and when driving was well and truly over boosting according to the boost gauge and was under powered.

I had a look roadside and couldn't hear any vaccum leaks do I turned my boost controller off, but that didn't fix the problem and is now obviously running less boost.

So I'm thinking it might be AFM. Are there any other obvious causes I have over looked.

Any advice is appreciated

Thanks

[Kane_R32]

What boost gauge? And what was the boost controller set at?

[RBrennan25]

It was over boost on both the standard gauge and the gauge on the eboost street I use for boost control. Both had the same pressure displaying. I just had it set on low boost which is 8psi. Then when I turned it off obviously it reverts to wastegate pressure

Weird thing is though I'm home now and about half an hour of driving later the boost came good again, completely back to normal even with the EBC on.

I'm doing a service on it tomorrow anyway (which is good timing haha) so ill do the spark plugs, O2 sensor, and have a look at the AFM and hopefully the problem won't come back again. Anything else that may have caused it or that I should look at tomorrow?

[RBrennan25]

Also looks as if there's a little bit of oil on top of the AFM and on the vacuum hose that connects to the intake manifold (I think I can actually see where it goes at the moment, I don't have my torch) it's only a little bit but not sure if that would help find the problem?

[jjman]

inside the AFM or actually on top of it?

also, no vacuum hose connects the afm to the manifold...

[RBrennan25]

Yeah my bad mate I didn't have any light, it looked like a vacuum hose in the dark haha

It's all good it turns out it isn't even oil, just the rubber hose is actually sparkly?? I have no idea why but in the light I had yesterday it just looked like oil had gotten out.

I'll do that big service today and that should clear it up

[Kane_R32]

So if its set to run 8psi, and its over boosting, what boost are you seeing on the Eboost when it over boosts?

[RBrennan25]

On a completely flat stretch of highway at 110 km/h it was at 3.8 psi. Definitely much higher than it should be. Shouldn't even be at positive pressure just cruising like that

[niZmO_Man]

Tried another AFM?

[Kane_R32]

Have you zero'd the eboost?

[RBrennan25]

Well today I cleaned the AFM, changed the air filter, and did spark plugs and it definitely runs better and the boost is back to normal. Just have to do the O2 sensor next week and I dare say that will resolve the problem. Could have been 1 or a combination of all of them