vrracing

iTrader: (1)

Since we have fuel pressure we are moving on to aggressive vacuum leak detection to find the cause of our pulsing and inability to idle. So we built a TMIC bypass and a fitting for the front of the AFM.

We used a generic spray bottle filled with bubble juice and starting at the AFM worked our way back spraying bubble juice as we went. We immediately found bubbles growing at the joint of the black plastic air intake pipes. So that's good.

But there seemed to be a really loud leak under the UIM. We sprayed bubble juice under the UIM near the secondary injectors but couldn't see any bubbles growing. You can really hear the air moving thru the TB and UIM. I thought maybe it was where the shafts come out of the TB so I sprayed those but they dont leak at all. I sprayed all the visible vacuum lines but couldnt see any bubbles.

Then on a whim I opened the throttle and the pitch of the sound changed. Hmmm...

I checked at the exhaust to see if anything was coming out. That Corksport being almost 4" in diameter could be so wide that the small volume of air we're pumping in could be completely dispersed. Plus the air injector isn't connected at the cat so it could be flowing out there too.

But air continues to flow from the compressor so it's going somewhere.

I made a video of the sound with me moving the throttle.


That sound is the air flowing from a full size air compressor at about 10 psi. As you can see, it flows at a brisk pace the whole time. When I move the throttle, the pitch changes.

Any ideas? Is this right or do we have a massive leak under the UIM?

If you think there's a leak under the UIM, and it turns out that there arent any vacuum lines popped off, could it be the injector o-rings are bad?

If I take off the UIM, is there a common way people pressurize the LIM to check the ACV, OMP injectors and fuel injectors? Given that there are 4 independant air passages it would seem I'd have to build a plate to block off the top of the UIM and then build an NPT manifold to distribute the air to each passage. Right?

As an aside, the OMP lines have filled with oil so there is vacuum being applied to them.

Thanks,

Jim

arghx

iTrader: (3)

how much boost does it hold on the gauge?

If the upper injector o-rings were bad, you would have a fuel leak. If the grommets at the bottom are bad, you would have a vacuum leak. Check all your OMP vacuum lines. Make sure you have the tightest possible vacuum hose on every barb-- 5/32" works best for many of them (like the OMP lines).



Here is a pic of a LIM pressure tester that an FD guy rigged up. There are separate holes tapped for each runner.

vrracing

iTrader: (1)

Oh cool, thanks Arghx. I'm glad to see that someone else has burned this trail before.

So in your opinion or what you've read, once the system fills with air, air should stop flowing right? It should be dead-*** quiet if there are no leaks?

vrracing

iTrader: (1)

Oh, and I dont have a boost gauge. I bought a gauge set to get rid of the PNRD21 display but that was early on in the process and I was ignorant. And I'm still ignorant, just less so!

88rxn/a

iTrader: (6)

http://www.boostpro.net/prodtester.html
i bought this one.....
i plan on doing a write up soon once i get pics of how i did it....these work so well!!
but think about it.....if you dont block off the exhaust....the air has to go somewhere....and did you check your oil fill neck to see if its leaking? i see in your sig you have all your emissions stuff on so the vent for the crankcase is sealed up correct....

arghx

iTrader: (3)

My car held 18psi without leaks. Yes, some air will go out the exhaust, but if there is a vacuum/boost leak you will hear hissing and feel air escaping. If it's not leaking, you will still hear the sound of air running through the system, but you won't be able to feel it or see it bubble up when you spray.