I've noticed a 3mm(approx) hole straight through the lower triangular section of the throttle body between the two throttle bores.

Is it supposed to be there and if so, what is it for?

 

That is the air passage for the IAC. It controls idle engine speed by opening and closing a small valve that is on the underside of the throttle body.

 

Thanks for the input, but I had the throttle body off the car to examine the IAC and to clean it, this was when I noticed the hole.

I identified the IAC ports but this appears to be completely unrelated to the IAC, its just a hole that allows air to flow straight through the TB and straight into the manifold, almost like someone has just drilled it?

Any ideas?

 

Its supposed to be there, just an idle air passage. Passes into a small hole in the intake manifold, and comes out in (8) smaller holes in each intake runner near the fuel injector boss.

 

I've managed to take a picture of the hole to clarify my question:

Throttle body hole

Two questions:

1 - If the IAC valve already controls the amount of air flowing through the IAC port, what is the purpose of having this unmetered hole?

2 - Would blocking the hole reduce idle speed?

Thanks!

 

The diameter of the hole determines a constant amount of idle air. It is a passage in paralell with the passage regulated by the IAC motor. Some people enlarge it to lower the IAC counts at idle after a cam install.



If you block it the IAC motor would compensate opening up some additional steps in order to maintain the programmed idle speed.