Boost leak; where from?

[xxraptor660xx]

I just boost leak tested my 1g for the first time. One coupler was loose, so I tighened it. I sill have anoher pretty big leak, but i don't know where it's coming from. The leak is so bad that the car is running really rough, and idles at a low RPM. I hear the pressure hissing out past the throtle body. Could it be the intake manifold? It holds 10psi only for about 3-5 seconds. I used windex, didn't see any bubbles, and I started the car and sprayed it with carb cleaner but got nothing. Anyone who can give me some advice, i'd really appreciate it. Thanks in advanced!

 

[jongreene]

Could be the throttle body shaft seals or gasket between the TB and the intake manifold.

Did you spray around there?

Maybe try some soapy water, id imagine itd be "bubblier" than windex.

 

[xxraptor660xx]

The gasket between the Tb and intake manifold is ok, I sprayed it. I think he car might be leaking from the bottom of the intake manifold, i'll jack it up and spray it.

 

[Cobrasatellite]

Same situation here
I just did my boost leak test and I think it went pretty good I only had like 1 leak per hose. so I will be replacing ummmm all of them. I figured 20 bucks or so for all new hoses is worth all the headacks it will save later. (all the Ic hoses were good but there gettin hard lines soon!

 

[xxraptor660xx]

How much VAC am I supposed to be at during idle? I know there's a leak because i used to be able to hold more vacuum. I'm now at -10ish and was at -25ish. Would a leaking intake manifold cause a boost leak?

 

[t25fury]

any kind of leak is bad,be it vacum or boost,its possible that your intake manifold gasket is old and leaking, but more comonly the throttle body shaft seals leak, what about the biss screw oring ?

 

[xxraptor660xx]

Well when the car is off and I did the boost leak test, it bubbled up..When i sarted the car it didn't seem to be leaking.

 

[xxraptor660xx]

Update: I just drove the car and there's deff. a leak. My question is would the intake manifold gasket leaking cause the car to not hold boost? I drove it and i didn't hit boost for like 15 seconds till the motor revv'd..

 

[EclipseGST-95]

95 percent of dsm's have a leak there just some are worse than others.... heres the website i bought the shaft seals from but never installed them my leak isnt that bad http://www.machv.com/throtbodseal.html you have to take off your upper ic pipe and elbow from the throttle body, disassemble your throttle cable, unbolt the throttle body from the intake manifold and unplug the plugs/hoses from the throttle body, take out the screws from the throttle plate/shaft take out the shaft replace the throttle seals and put it all back together..... as for those screws i believe they are locktited in and you can damage the screws, the threaded holes, the shaft, or all of the above. The dealership recommends an entire replacement of the throttle body because the dealership wont replace the seals...maybe its a scam i dont know but it's been done before here http://www.vfaq.com/index-main.html and here http://www.vfaq.com/index-main.html

 

[EclipseGST-95]

also when replacing those screws with new ones you must lock tite the new ones in... if they were to come out when the cars on you will probably have some serious internal damage

 

[xxraptor660xx]

Thanks but I want to find out where this big leak is coming from, i'll probably replace that after.

 

[EclipseGST-95]

that is the leak... your cars 15 years old... if you compress air in your pipes again and push the throttle open and close you should hear the air leaking make differnt noises... throttle body shaft seals... its the same reason you probably have a throttle that sticks open on warm days causing a higher rpm "idle"

 

[romeen]

How much VAC am I supposed to be at during idle? I know there's a leak because i used to be able to hold more vacuum. I'm now at -10ish and was at -25ish. Would a leaking intake manifold cause a boost leak?

Normal idle vacuum is 18-22 inHg. Your readings are consistent with a good size leak. Yes a leak at the IM gasket will be a boost leak when boosting and a vacuum leak when under vacuum.

Although you may very well have leaking shaft seals (sound/pitch of leak will change as you rotate the throttle butterfly by hand) as talked about, in my experience these leaks are usually not severe enough to cause the significant driveability issues that you are describing. If you hear rushing out near the TB but can't locate it then check your EGR valve and the hose associated with it. It can be easy to miss because of it's location beneath the TB.

Of course there may be other issues but these would be a good place to start.

 

[Black_Bullet]

I generally idle at -20 with 900 rpms.
Two places that tend to cause boost leaks for me after I fixed all the rest were
the injector seals and the tb shaft seal... I fixed the injector seals and it helped,
the car even gained like 5% injector duty cycle back? But i still havent fixed my final leak
which is at the tb shaft seal or somewhere on the tb its leaking....

 

[xxraptor660xx]

Thanks for the replies guys, i'm gunna head down to my shop later tonight and boost leak test her while shes on the lift, that way I can see the bottom of the IM.

 

[EclipseGST-95]

i dont think you can see the bottom of the intake manifold when its on a lift... either way best of luck let me know if i was right about the shaft seals needing replacement

 

[xxraptor660xx]

Im going to test it tomorrow.

 

[xxraptor660xx]

Well i was messing around with the boost controller and I turned it down to almost 0psi of boost. The car revs all he way but still hesitates a little bit. When I turn it back up to 16psi i barely runs. What could this be?

 

[EclipseGST-95]

maybe u should check to make sure u have good connections on your avc-r are they tied into the ecu at all?

 

[xxraptor660xx]

Yeah all the connections seem to be ok. Thanks everyone the car runs better now, your help is greatly appreciated!