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52 MM TB vacuum question

1K views 11 replies 5 participants last post by  The Pope 
#1 ·
Im installing a 52mm TB on my T2. The stock TB has 2 Vac ports, obviously one is ported and the other is manifold vacuum. However, the 52 mm that I have only has one vacuum port. It looks like its manifold vacuum only. If I install both the charcoal canister lines to that one port, using a vacuum tee, will that throw a C/E light or give problems? The canister will now be running on manifold vacuum only instead of manifold AND ported vacuum like the stock setup. thanks
 
#2 ·
Both lines from the TB ports run to the same line. :confused:

Not exactly sure what they are trying to accomplish with this vacuum setup other than they do not want the canister to purge at idle.

Remove the line from the canister, is there vacuum present at idle with the stock TB?
Is there vacuum present when you open the throttle?
Install the new TB and connect both lines to the single port and repeat.
What were the differences?

Connected/disconnected, either way this will not cause the CEL to illuminate, OBD1 only knows if the purge solenoid is functioning electrically, it knows nothing about vacuum routing or leaks/restrictions in the evap system.

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#3 ·
i know improbably wrong, but since vacuum is highest at or near idle, wouldn't that canister purge at idle and NOT while the motor is under load? Either way, I will do what you said and see the results. thanks alot
 
#5 ·
i know improbably wrong, but since vacuum is highest at or near idle, wouldn't that canister purge at idle and NOT while the motor is under load? Either way, I will do what you said and see the results. thanks a lot
:error:



As it turns out...
I, I, I was wwwwwroooong. :eek: :bash: :bang head :eek:mg: :shocked:



I still have no idea why the two lines are run together, been over thirty years since I had "principal and theory" on these cars.

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Auto part Automotive engine part Transmission part Axle part Transfer case part
 
#7 ·
One nipple is before the throttle plate, the other is after, so on closed throttle there is momentary pressure differential. I thought both were the same source (well they are kinda sorta). I figured this out recently messing with my BOV set-up - if it helps at all with this. On the 2.2T/2.5T the large nipple is after the throttle plate (manifold side)
 
#12 ·
I have a 52 I could sell you. Normally little one goes to BOV and we plug the larger one. Also as many know stock replacement adjustments the throttle is adjusted for a V6. So remember to plug any larger AIS hole and unplug the manual adjust screw and adjust the idle warm mechanically at 950. Then hook up the AIS to have the idle right. Bouncing RPM is a good sign you're not adjusted right.
 
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