I finally made it back to the little island, and spend some time hunting the sound of leaking vacuum, which I heard since the car came back replacing coolant hoses.

Found the vacuum hose for the throttle body laying loose, so that is fixed.
Also took the opportunity to take the slack out of the throttle cable.

However, on blipping the throttle, I hear a 'rasping' sound.
It appears when I blip, last some 1/4 of a second from idle, and disappears either if the rpm goes up, or if I let loose.
It happens each and every blip, and I can locate it coming from under the middle of the intake in the middle of the engine.

Can't figure out if it is left or right.
I do not think it is a chain due to the location, but I also do not completely exclude that due to the sound.

Any ideas?

Eric

 

See the hose at the top of the Left side valve cover? Check it close, they sometimes melt to the block. Real pain to change. Worth a look. Otherwise, the 4.0 engine does make a bit of a hiss sound, only noticeable with an open bonnet. Any other issues?

 

Might be a loose baffle in the exhaust. Goes it happen in a particular rev range, say about 2000 - 2500 rpm when you are driving?

 

Saw both your reply, but did not have time to check anything further yet.

I can't imagine it is exhaust related, too far away.

Judged by the blipping, I tend to think it is a leak, but judged by the sound, from the sound it iI am afraid it is metal to metal.

It really only occurs for a split second, only if you blip the throttle, and goes away immediately when the rpm goes stationary.
I can only hear it with the bonnet open.

If I have some time next week, I will try to see if I can pinpoint the location better, as I suspect there is not much under the intake manifold which can cause this .... I hope it is not a distribution chain.