I finally got my XJ-S back after having quite a bit of work done and took it out for a nice, 75 mile shakedown cruise. When I got it home, I found a thin tube disconnected from the intake manifold and leaning against the air filter housing (photos attached).

I've reconnected it but I'm wondering if someone can tell me what that tube does and, maybe a theory about what disconnecting it might have done to the car (if anything)? Is it a vacuum hose for something?

Thanks in advance,
Rhett

 

If you follow it back I'm pretty sure you'll find that it goes to the fuel pressure regulator. But, I make no claim to having memorized all vacuum hoses on a V12 Jag


Cheers
DD

 

And since it appears to be the RH throttle body, you can also (in addition to just plugging it back in) just cap the nipple and forget about it. In fact you can remove the entire RH fuel regulator assembly and never notice a difference. Apparently even Jaguar gave up on it after a while and eliminated it. I've been running my '87 XJ-S without it for over a year.

I originally removed mine because the diaphragm inside had cracked and it was leaking fuel into the vacuum line. If you ever run into that situation, don't waste your money on replacing the regulator, just bypass it.

Cheers,

John
1987 XJ-S V12
64,000 miles

 

my vote is that it goes to the brown vac regulator. on the top "port" line for the vac advance unit.
that's what mine is plugged into.

 

I plugged it back in. We'll see if it makes any difference in how the car runs. Thanks guys .