Missing vacuum line ? | Ford Explorer Forums - Serious Explorations

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Missing vacuum line ?


New Member
August 18, 2007
Reaction score
City, State
Sheboygan Falls, WI
Year, Model & Trim Level
1991 XLT
I been working on a 1991 Explorer. I discovered a vacuum line was off the "tree" , but I could not locate the missing line. I plugged the port and the engine is back to running well but the gas mileage is way down.

The diagram posted here and the underhood map all show 3 lines originating at the tree but in reality there are 7 ports.

So does anyone have a "complete" vacuum map available ??

Thanks in advance

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The EPA diagrams only show the environmental connections.
Keep an eye out for transmission fluid. There's a common problem where the Automatic Transmission Vacuum Modulator goes bad and blows the vaccum hoses off.


  • Vac Ports.JPG
    Vac Ports.JPG
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Thank you very much - it appears that my capping the port was correct. Now I just have to figure out why I have a mileage drop......:confused:

I would start by checking the vacuum lines to be sure they aren't blocked, leaking or disconnected at the other ends (where they connect to the components away from the tree).


I checked all the obvious connections this morning, need to do a full trace as
I do have slight differences in the actual set up off the tree.
I only have one "capped" port vs 2 in the picture.

I am going to do another code scan after I check the lines to see if any of the previous have returned.

I should add that to the pic. This is a manual. The automatic transmission uses one of the ports.

Common vacuum leaks are the lines that cross the engine bay get brittle and break. Also around the grommet on the brake booster.