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81 SC Air Box & Vacuum Leaks
I acquired an 81 911 SC Targa with about 65K and I've been unraveling issues for months. Having the other "must do's" completed, I'm now knee-deep into the CIS.
The short story is... after I replaced the fuel filter and fuel filter and accumulator, the engine would load-up/flood after it had sat for an hour or more. I did fuel pressure tests and everything was within spec. The WUR and Aux Air Controller appear to be operating correctly. When I leaned out the mixture, that helped with loading-up issues but, that caused other issues and it ran way to lean. I replaced the injectors thinking they might be weeping but that didn't help with the flooding issues. I live in SoCal so the climate is extremely mild but, at different engine temperatures, the car would run and idle significantly different leading me to believe there was either a crack in airbox or an air leak that expanded as the engine compartment became warmer. I used starting fluid and sprayed in different areas and found that there was a very, very slight increase in rpm's by the throttle valve body at the gasket area. The current plan is to thoroughly inspect the air box for cracks/leaks, re-gasket & re-seal the parts connecting to the Air Box along with runner boots. Since I'm there I'll replace the seals, gaskets, and hoses in the triangle of death. When I looked at the bottom of the Air Box I notice this hole in the bottom (see pic) with no apparent hose going to it. The P/O had the Air Box replaced p/n 911.110.104.20, later boxes also have the same hole in the bottom. Is this supposed to be plugged or a hose attached? My unit.  A better rendition of same p/n.  Are there other things I should address or inspect while in there? The Air Box has a pop-off valve installed. Any insights would be appreciated. BTW: It is possible to take the CIS out without relocating the A/C compressor but, I don't recommend it. Don't ask me how I know! Regards, dugr |
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03-05-2020, 01:58 PM
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Registered
Join Date: Mar 2018
Location: LA
Posts: 64
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You are in for the long haul! I am no expert but I've been fixing leaks and dealing with mixture for the past year or so. For me, I've determined that the pop off valve was poorly installed and leaks more or less depending on temperature. Check the epoxy and o ring for cracks. I plan to reinstall a new one one of these days... add it to the list!
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03-05-2020, 02:06 PM
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Hole is for drainage of any crud which gets in there. Not the source of your issues.
Cracks ? 
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03-05-2020, 03:46 PM
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Quote:
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03-05-2020, 03:58 PM
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Still here
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Yeah, check the entire unit for vacuum leaks. Given it's out, the runner ports on airbox and the breather hoses should be plugged for the test.
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03-06-2020, 12:02 PM
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Black Label
