Nissan 240SX Forums banner
1 - 4 of 4 Posts

·
Registered
Joined
·
83 Posts
Discussion Starter · #1 ·
He guys, sorry to ask such a stupid question, but I can't seem to figure out why my boost gause is reading 250 mmHg. Now I'm unsure why its reading so low, my car runs incredible, I have excellent compression across the board, so I'm wondering what you all see at idle in your rb's so I know what I should be seeing, and ill start seeing what's up, I'm thinking my boost gauge is innacurate. But I can only hope, its probable a leak, but it shows a solid 30 psi of boost when I'm on it, and its tuned at 30, my a/f is spot on at 12.5 under load with 73.4% injector duty cycle.
 

·
Registered
Joined
·
31 Posts
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?
 

·
Registered
Joined
·
83 Posts
Discussion Starter · #3 ·
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 ?
 

·
Registered
Joined
·
31 Posts
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 ?
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.
 
1 - 4 of 4 Posts
Top