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Join Date: May 2006
Location: Atlanta, GA
Posts: 56
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Spring Loaded Plunger
I understand the mixture adjustment screw, but what is the function of the spring loaded plunger? Does turning it do anything? What does pushing it down do?
I tried to slightly lean my enigine due to an almost failed emissions test, and now it does not idle right. If you adjust the mixture to you have to reset the idle? |
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06-17-2009, 07:46 AM
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I am not sure what that plunger is for, either, though I suspect it ahs to do with cold starting.
You do have to reset idle after adjusting CO.
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Emery 1988 930 coupe - Silver Metallic TurboKraft 3.3L 8:1 CR, SuperSC Cams, GT35R, B&B Headers, TK intercooler, Tial WG, ARP, tecGT based phased sequential EFI & ignition, Wevo shifter/coupler, ... 
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06-17-2009, 09:15 AM
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Join Date: Oct 2003
Location: Mount Pleasant, South Carolina
Posts: 14,330
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If we are talking the same thing, the spring loaded part keeps the tension off. I've JB Welded a small allen wrench in mine to make it easier to get to.
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06-17-2009, 10:34 AM
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Location: Central Washington State
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That idle CO adjuster is on a spring loaded post to keep it from engaging with the actual adjusting screw inside the head. You have to push it down until it meets resistance, then turn it as it engages. And if you push down too far, it will start to deflect the arm and cause a rich mixture, so you have to use a gentle touch when making any adjustments with the engine running. And yes, depending on how much you adjust the CO%, you may have to re-set the idle with the air correction screw.
If you don't push it down, you can turn it to your heart's content and it won't do anything.
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Mark H. 1987 930, GP White, Wevo shifter, Borla exhaust, B&B intercooler, stock 3LDZ. |
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06-17-2009, 11:13 AM
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Join Date: May 2006
Location: Atlanta, GA
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So, you are saying that the 3mm mixture screw
and the spring loaded plunger are the same? Gently pushing down and turning and turning with a 3mm allen wrench do the same thing?
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06-17-2009, 05:58 PM
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Join Date: Jul 2008
Location: Central Washington State
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Quote:
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Mark H. 1987 930, GP White, Wevo shifter, Borla exhaust, B&B intercooler, stock 3LDZ. |
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06-17-2009, 06:21 PM
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Join Date: Oct 2003
Location: Mount Pleasant, South Carolina
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Yes. The plunger is really a hollow tube that allows you to insert an allen wrench into it and then push down to engage the adjusting screw.
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06-17-2009, 06:23 PM
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beancounter
Join Date: Jan 2008
Location: Weehawken, NJ
Posts: 3,593
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Funny story about the "plunger":
When I bought my car, the PO told me that he had the car at the shop for emissions testing and the wrench told him that the mixture adjustment screw was "broken" and the engine needed to be dropped to fix it. I have discovered that the mixture adjustment screw is just fine. I guess the wrench didn't realize that you have to push the thing down in order to make the adjustment. Supposedly he was a Porsche mech, but I suppose he hadn't touched many turbos in his career  This is why I try to DIY as much as possible.
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Jacob Current: 1983 911 GT4 Race Car / 1999 Spec Miata / 2000 MB SL500 / 1998 MB E300TD / 1998 BMW R1100RT / 2016 KTM Duke 690 Past: 2009 997 Turbo Cab / 1979 930 |
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06-17-2009, 07:55 PM
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All the manuals I have do not mention the spring loaded plunger being the CO adjsutment. They mention the CO adjustment being blocked by a cap for US cars.
I'm glad this thread cleared it up because I was overlooking the spring loaded plunger and could not find the friggin' CO plug. Now I get it! Call me Captain Obvious 
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Emery 1988 930 coupe - Silver Metallic TurboKraft 3.3L 8:1 CR, SuperSC Cams, GT35R, B&B Headers, TK intercooler, Tial WG, ARP, tecGT based phased sequential EFI & ignition, Wevo shifter/coupler, ...
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06-18-2009, 05:13 AM
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