vaccum on an rb20

When I first picked up my 240 it was only pulling about the same vacuum as yours at idle, 10" - I felt it was low but since the idle was pretty stable, I didn't investigate any further. When disassembling for a few broken exhaust stud extractions I found many sources for vacuum leaks. particulary the lower to upper intake gasket and to a lesser degree, the Cold air valve
Put it all back together with no other changes aside from having all exhaust studs instead of just 9, I had 15-17" of vacuum at idle. I made no other adjustments, aside from the screw on the USDM passenger side of the IACV.

I tried spraying Ether/Starting fluid around the major sources for vacuum leaks, listening for idle speed changes but got no results. maybe you will have better luck?

Thanks man, I did find a leak on my upper and lower gasket, where's the cold air valve, sorry to ask suck an ass dumb question, but idk where its located or are you talking about the idle air control valve ?

Rb20Hatch said:

Thanks man, I did find a leak on my upper and lower gasket, where's the cold air valve, sorry to ask suck an ass dumb question, but idk where its located or are you talking about the idle air control valve ?

Click to expand...

It's the piece that bolts right to the backside of the upper intake plenum. It has the brake booster port near it and the air tube from the cold air valve Ts off into it and the intake tube.