SOLVED - what is this Vacuum line connection on throttle body?
#1
Nordschleife Master
Thread Starter
SOLVED - what is this Vacuum line connection on throttle body?
Update: Solved - its a factory test-line.. see photos further down this page
Hi all,
Hopefully someone can identify this vacuum line off the bottom of the throttle body I'd love to finish putting my intake together today!
First, some basics.. my car is an '89 5-speed, so has the superior simplified vacuum system compared to the auto 'box
I've scoured the WSM and various write-ups, and have page 24-216 printed on A3 to make it easier to read.
I've accounted for the following connections and have them made off the two vac connectors on the top of the throttle body.
3x fuel pressure regulators
1x air-pump diverter valve
1x charcoal canister diverter valve
Looking at 24-216, I can't see anything else that needs vacuum other than the flappy, which takes ported vacuum from the reservoir, not manifold.
So where does this vacuum line in the picture below go to?
Thanks!
Hi all,
Hopefully someone can identify this vacuum line off the bottom of the throttle body I'd love to finish putting my intake together today!
First, some basics.. my car is an '89 5-speed, so has the superior simplified vacuum system compared to the auto 'box
I've scoured the WSM and various write-ups, and have page 24-216 printed on A3 to make it easier to read.
I've accounted for the following connections and have them made off the two vac connectors on the top of the throttle body.
3x fuel pressure regulators
1x air-pump diverter valve
1x charcoal canister diverter valve
Looking at 24-216, I can't see anything else that needs vacuum other than the flappy, which takes ported vacuum from the reservoir, not manifold.
So where does this vacuum line in the picture below go to?
Thanks!
Last edited by Hilton; 04-18-2008 at 10:55 PM.
#2
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almost certain that one goes to the airpump diverter valve. the line coming off the top of the throttle body towards the rear should have a 4 way splitter with lines going to both dampers and the pressure regulator. the 4th line is plugged (goes to auto trans in the autos.) the forward line off the top goes to the charcoal cannister valve (fuel tank vent.)
#3
Nordschleife Master
Thread Starter
almost certain that one goes to the airpump diverter valve. the line coming off the top of the throttle body towards the rear should have a 4 way splitter with lines going to both dampers and the pressure regulator. the 4th line is plugged (goes to auto trans in the autos.) the forward line off the top goes to the charcoal cannister valve (fuel tank vent.)
The forward line off the top is the same as you say - also confirmed from the '88 5-speed.
This has me stumped.. unfortunately on his car we can't see the underside of the TB, although he's coming round here later so I might yet be able to spot it emerging from the intake somewhere. A fresh pair of eyes may spot the connection too I'm hoping.
I could just plug it, but I'd hate to discover that the car wasn't running right after putting the whole intake back together
#4
Burning Brakes
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I'm fairly confident that on my 87' this went to the air pump diverter valve. Looking on page 24-216 of the WSM it seems that the vacumm line coming from the under side goes to "I" which is called the " Secondary Air Valve" which I am assuming is the valve we are discussing?
This page in the WSM clearly show where the other 2 vacumm lines off the underside of the intake go to and its not the air pump system. I had this line pluged on mine as the air pump had been removed.
This page in the WSM clearly show where the other 2 vacumm lines off the underside of the intake go to and its not the air pump system. I had this line pluged on mine as the air pump had been removed.
#5
Nordschleife Master
Thread Starter
Logic therefore says that the bottom line went to something else... but I can't think of anything else that takes manifold vacuum on the car?
Anyone able to think of any other devices on a 5-speed that take manifold vacuum other than the charcoal filter, air pump, and 3 pressure regulators?
jon928se is getting here shortly and I'll be examining his '88 SE closely to check all the lines, so hopefully we'll find the answer using a mirror to peer under the TB.
#7
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That's the feed for the special valve that allows the 5 speed to simulate the power of the automatic by induced direct injection - this was omitted from the WSM to elude the not so clever owner (not you of course Hilton). If you do not connect it to the correct nipple your car will revert back to being a boreing low powered 5 speed exactly as it was delivered from the factory.
I strongly suggest you drink at least two glasses of a good Australian red before attempting this complex manouveur 8>)
I strongly suggest you drink at least two glasses of a good Australian red before attempting this complex manouveur 8>)
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Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission? George Layton March 2014
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Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission? George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
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#8
Nordschleife Master
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#11
Nordschleife Master
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Mystery solved with the help of Jon's SE!
After removing his airbox and MAF and poking around with a mirror, we found it on the underside of the throttle body, and then figured out where it goes.
See the photos below - it appears to be a test port with a large rubber cap on the rear end of the RHS valve cover.
Jon's air pump valve and charcoal valve are both the same as mine (also factory - his intake hasn't been apart since manufacture).
Here are photos.. one of the line as viewed from above with MAF removed, and one of the end of it with the cap.
This probably explains the slightly high idle that I took my intake apart to fix.. mine had no cap on the line at the testing end
Oh well.. at least I know all my rubber is new and good for 20 years.
After removing his airbox and MAF and poking around with a mirror, we found it on the underside of the throttle body, and then figured out where it goes.
See the photos below - it appears to be a test port with a large rubber cap on the rear end of the RHS valve cover.
Jon's air pump valve and charcoal valve are both the same as mine (also factory - his intake hasn't been apart since manufacture).
Here are photos.. one of the line as viewed from above with MAF removed, and one of the end of it with the cap.
This probably explains the slightly high idle that I took my intake apart to fix.. mine had no cap on the line at the testing end
Oh well.. at least I know all my rubber is new and good for 20 years.
#12
Burning Brakes
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Sorry for my confusion, but I do remember now. When I deleted my air pump I also deleted that test port and pluged that line.
Thanks for this info.
By the way Roger we are about 3 BomBay's into it here on the Beach, its 10:20 and a full moon!
Thanks for this info.
By the way Roger we are about 3 BomBay's into it here on the Beach, its 10:20 and a full moon!
#13
Hi Hilton
Confirmation. My '89 RHD has the same line, blanked off with the same type of cap. Somebody else here (Worf?) told me it's a factory test port. BTW does your car have the 7-port vacuum tee? (Source + 6).
Colin. 89GT.
Confirmation. My '89 RHD has the same line, blanked off with the same type of cap. Somebody else here (Worf?) told me it's a factory test port. BTW does your car have the 7-port vacuum tee? (Source + 6).
Colin. 89GT.
#14
Nordschleife Master
Thread Starter
No it has the 5 port Tee. ATs have the 7 port.
#15
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That 'factory test port' does not attach to the vacuum system at all. It's an exhaust gas sample port from the headers upstraem of the cats, used to adjust mixture/CO. One on each side of my engine.