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Unknown intake tube

625 views 6 replies 3 participants last post by  Stretch 
#1 ·
Can someone identify the tube that is an off-shoot from the breather hose in the picture.
It disappears under the air filter and I'm too lazy to pull off the filter canister to have a look.
Mine is a 2.6L engine.

Anyway it has a profound effect on idle roughness and low RPM "sputter"

Your help would be appreciated.
 

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#2 · (Edited)
It provides vacuum to the fuel pressure regulator. Apparently it is a failsafe for if the diaphragm in the FPR fails.
 
#3 ·
Thanks A.Cabral. Yes the W124 guys also mentioned a similar purpose. The vacuum diagram I found confirms that it is connected to some sort of a switch in the fuel distributor area.

So it is not actively doing anything during normal operation. I'm still very surprised that a very small leak there causes such engine roughness.

I'm going to do a controlled experiment to replicate this by taking out the Teflon tape and see if the unhappy idle and low RPM roughness comes back.

I'll report on this later.
 
#4 ·
Does the roughness occur with the vacuum line plugged into the breather or disconnected?
 
#6 ·
Should be nothing unless if fuel is leeching out of your fuel pressure regulator. I've run my car with the breather off before and don't recall having an issue, but keep in mind that my car is beat to hell.
 
#7 ·
Some times a bit of aerospace303 does wonders for dried out rubber bits on these cars - leaks on these systems often cause havoc - sometimes it is just time to replace the rubber though...
 
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