No Vacuum At Idle

[Waderzila]

Hey guys,

Have a little newb question here, I started my car yesterday and noticed I didnt have any vacuum when idling, it shows just above 0 on my boost gauge(aftermarket), but when i rev it it goes down. Would this be a vacuum leak? would this be related to the CAS, cause I advanced the timing a little bit to trouble shoot the sputtering.

My factory gauge is plug in behind the balance tube, but doesnt read a thing, might be broken.

And my greddy is tapped in the vacuum underneath the FPR, that goes from the throttle chamber, under the tb cover and to the canister.

The purple one on this diagram:

I also plugged my greddy behind the balance tube before and it wasnt reading a thing, would there be something wrong with a boost source going to the balance tube.

Any help would be appreciated.

R32 GT-R

Thanks

Edited April 27, 2009 by Waderzila

[VB-]

where is the vaccum line from the guage run to? before or after throttle body? car probly wouldnt run if there was no vaccum....

[wombat_1988]

how smooth does the car run? mine is a little similar to that and i've blown the inlet manifold gasket

[PIOTREK]

dude i don't think that u should be having vac on idle, only when the car is running (Aka driving [moving})

[VB-]

^no, vac should be there all the time, highest at idle/sharp closing of the throttle, and dropping as the throttle is opened more

[PIOTREK]

^no, vac should be there all the time, highest at idle/sharp closing of the throttle, and dropping as the throttle is opened more

just checked, zero on idle- afm boost guage

[femno]

What?

You cant possibly have zero vacuum on idle...the engine wouldnt be running if there was zero!

You must have a hole in the hose somewhere, or its unplugged...try getting someone to suck/blow in the hose and you read the guage.

[Waderzila]

where is the vaccum line from the guage run to? before or after throttle body? car probly wouldnt run if there was no vaccum....

Well the aftermarket one is tapped into the vacuum underneath the FPR, that goes from the throttle chamber, under the tb cover and to the canister.

The purple one on the diagram.

And, my factory gauge is plugged in behind the balance tube.

The car runs like a dream, boost fine and idle great.

[Waderzila]

where is the vaccum line from the guage run to? before or after throttle body? car probly wouldnt run if there was no vaccum....

Well the aftermarket one is tapped into the vacuum underneath the FPR, that goes from the throttle chamber, under the tb cover and to the canister.

The purple one on the diagram.

And, my factory gauge is plugged in behind the balance tube.

The car runs like a dream, boost fine and idle great.

[sonoramicommando]

there are two lines going to the canister, if you have the gauge hooked up to the one below the throttle body, it won't work.

how are the hoses to and from the canister plumbed, if you are using one of them for boost gauge?

[SATO GTS]

There is a vacuum/boost port right above numer 6 inj .

Hook into that and you will get a better reading .

[__PhaseShiftDown]

Currently, my boost controller (vac source) is T'd into the vacumn line beneath the fuel reg (pink line), and it does not read vacuum on idle, it reads zero. When I put my foot down, it will read vac for a little bit, then builds boost as normal. My stock boost gauge on the other hand reads vac on idle, sits above 7 on the stock boost gauge and goes up normal when I put my foot down.

I use to have my vac source T'd from the fuel reg line (and it reads the same as the boost gauge), but my understanding was thats its not the best place to T into, although I've been driving around like that for a while and car was running fine. Last week my engine developed an air leak from the throttle body, so I took the car to Bel Garage to have them fix it up and I also asked them to fix up the vacuum line. When I got the car back, I can see that they T'd the vac source from that line below the fuel reg line and it does not read vac anymore on idle. Car runs fine.

In either case, you should definitly get vac reading on your stock boost gauge when car is on idle. When you put your foot down, the gauage should move up to neutural then build positive boost pressure. If you don't get any vac reading or boost reading on your stock boost gauge, replace the vac line that goes to the sender.

Edited April 29, 2009 by __PhaseShiftDown

[Waderzila]

there are two lines going to the canister, if you have the gauge hooked up to the one below the throttle body, it won't work.

how are the hoses to and from the canister plumbed, if you are using one of them for boost gauge?

I have the gauge tapped into the purple-pink one on the diagram on the plenum side and my boost controller is plugged into that same line but on the turbo side of the motor. That line is not the one below the throttle body.

Edited April 30, 2009 by Waderzila

[Waderzila]

In either case, you should definitly get vac reading on your stock boost gauge when car is on idle. When you put your foot down, the gauage should move up to neutural then build positive boost pressure. If you don't get any vac reading or boost reading on your stock boost gauge, replace the vac line that goes to the sender.

My stock boost gauge is plugged into the boost port under injector 6, and is not reading anything. Maybe the vac line is broke, but i remember trying my aftermarket gauge on that same boost port and it wasnt reading anything either. Would there be a problem with that boost source?

Im just trying to figure out if I have a vacuum leak-boost leak.Tonight, Im gonna plug my aftermarket gauge on the fuel pressure regulator line and see if I have vacuum. Ill let you know what happens.

Thanks again

Edited April 30, 2009 by Waderzila

[peter_fc]

Sounds like you have it tapped into the wrong place.

Why dont you tap into where the factory guage gets its reading from. Its at the back of the balance tube at the firewall side of the vehicle and runs to the black box near your brake booster.