Replacing my head gaskets on a 2001 D2 with 175K miles.
While preparing to remove the intake manifold I could identify two of three ports on the passenger side. The port that is pointed to by the red arrow has no hose attached. Can anyone tell me what it is?
Thanks!

 

SAI control valve. It splits to both sides of engine through a small hose usually wraped with plastic cover.

 

Thanks. My 2001 D2 does not have SAI so is the port just plugged?

 

yes..

 

If That inlet is wide open then you have to cap it off; I can't see from the picture

 

thata also the port most people use to kill all the mosquitoes in their neighborhood

 

It should be capped. If not I'd expect you'd be getting lean codes (P1171 & P1174) due to unmetered air entering the intake manifold, which would likely hurt gas mileage as the ECU tries to add fuel to get to the designed air/fuel ratio. It's interesting to me that the '99-'02 DIIs have that port since I think SAI wasn't introduced until 2003. I might be wrong about that; California trucks may have had SAI from the beginning. I'm just grateful my truck doesn't have SAI.

 

Cute.

 

Well that seafoam induction cleaning. I call it skeeter killing

 

I understood the reference, I just wondered how many of the newbies do.