Problem while decelerating in gear at high revs

[Scullboy19]

So I have a vs 5 litre hsv enhanced manual and when I'm in like second gear and high revs, itll shutter like it's about to stall when im off the throttle but as soon as I add acceleration it's fine which makes me think it's not a fuel issue. Not sure what could be causing the problem but it can be real annoying, also it doesn't do it while im already low in revs only when high in revs

 

[greenacc]

How well kept is this engine?
Could it be a super dirty throttle body choking it, or an air leak at the manifold?

 

[Scullboy19]

How well kept is this engine?
Could it be a super dirty throttle body choking it, or an air leak at the manifold?

Well if it was either I would say it would drive like absolute **** but only does it high revs off throttle but goes away with throttle, it really just shakes the car violently but as soon as I accelerate it goes back to, I can't even try and keep speed at high revs but normal like 1 and a half to about 3 it won't do it

 

[Draimond]

So the engine is in deceleration at high rpm, there's no load on the engine and the throttle body is closed.
If I'm following right?

The only place it can get air in that moment is through the IAC?
Unless the butterfly valve can't close properly.
My guess is it's not getting enough air at high rpm with no throttle.

It's not fuel because it would struggle to get into high rpm.
And it's probs not spark because it would struggle under load.

 

[hademall]

That sounds feasible. Be good to know from the OP, although it's been a while since he posted

 

[Deuce]

@Scullboy19 the only other thing I would suggest you look over is engine/trans mounts and the harmonic balancer for slippage.

 

[Scullboy19]

So the engine is in deceleration at high rpm, there's no load on the engine and the throttle body is closed.
If I'm following right?

The only place it can get air in that moment is through the IAC?
Unless the butterfly valve can't close properly.
My guess is it's not getting enough air at high rpm with no throttle.

It's not fuel because it would struggle to get into high rpm.
And it's probs not spark because it would struggle under load.

Yeah, that sounds like it could be the problem tbh, how would u check that tho or even fix that if it is that cause yeah, it does feel like it's being chocked, like it's about to stall but because it's such high rpm it shakes more violently then say if it was actually about to stall

 

[greenacc]

Yeah, that sounds like it could be the problem tbh, how would u check that tho or even fix that if it is that cause yeah, it does feel like it's being chocked, like it's about to stall but because it's such high rpm it shakes more violently then say if it was actually about to stall

Clean out the IAC valve with throttle body cleaner. Don't play around with it or try to adjust it by hand, just clean out the valve and the air passage if it's blocked up. It would have to be broken or almost completely blocked to cause your problem I'd think..