Project LOLTRAC, or ST185 BS - a USDM Alltrac restoration

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Re: Project LOLTRAC, or ST185 BS - a USDM Alltrac restoratio

Postby Junctrac » Tue Jul 09, 2019 1:16 am

EvilStig wrote:Any pressure I put into the intake is lost unless I plug this hose up here. This recirculates back into the intake after the MAF but before the turbo. If I plug that hose, I can build pressure with the boost leak tester. I'm not sure what this is supposed to be, but I'm relatively sure it isn't supposed to be dumping boost out of it.


Sounds like crankcase vent. The pressure is bypassing piston rings and coming out that tube but shouldn't be much flow, especially when running, if it seems like a lot is coming out i would do a compression test if you haven't already. If there's any valve overlap with where the engine rotation ended up there could be pressure going out the exhaust too.
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Junctrac
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Re: Project LOLTRAC, or ST185 BS - a USDM Alltrac restoratio

Postby Junctrac » Tue Jul 09, 2019 9:41 pm

Sorry I lied, the hose closer to the front of engine connecting to valve cover is crankcase vent. The other one goes to idle up as you said and IAC valve under TB and somewhere else too i think. So if the IAC is still open at all then that's where the pressure was going. Im not sure when if ever the IAC is supposed to be 100% closed. The manuals have lots of testing procedures for the EGR valve etc. and probably the IAC, maybe that's related to your idle issue? I may have missed it but i didn't see any details about your idle issue, does it never seem to change it as it warms up?
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