Thread: Disco 1 '94 3.9L Missing hoses

First one under plenum is a throttle body heater which leaks after a while and unneeded in OZ. Its to prevent throttle body icing in UK in winter.

Second should go to either a vacuum pump in the LH battery tray or to a vacuum source. RRCs had a globe/sphere which had non return valves in it to run the heater flaps when low vacuum and the cruise control went off that if aftermarket. The later factory ones had a vacuum pump in the second battery tray.

Regards PhilipA

Thanks for that! It seems the reason I can’t find where it plugs into is the vacuum pump is missing. The electric plug is there taped up so I guess that now goes on the list...

cheers

Assuming that your ignition timing is correct and the vacuum advance is working, ( suck on removed tube.).

A couple of simple things to start and maybe get it running a bit better.

1. There is vacuum hose at rear of plenum for the fuel pressure regulator, these often wear or split at the end, check hose end etc.
clean end and suck on hose, this will tell you if diaphragm working ok, suck and block with tongue, you will tell.

2. If the intake system is dirty etc. you can adjust the base idle screw, located top of plenum, sometimes blocked by a plug, which needs removing first. then use a small allen key to adjust. There is a method described in rave, which involves blocking hoses etc. but I just do this.

If it's hunting or surging at idle, (rich) unscrew about a quarter of a turn at a time, it lets more air into system, check idle. If you unwind too far it will rev high when starting, but will settle down once the Idle control takes over. On my disco, it was idling up and down and stalling sometimes at lights, adjusting the base idle out a quarter fixed that. On another vehicle it had to be over a half turn out, it revved high at first. We reset base screw after removing plenum and throttle body and gave everything a good clean, things were a bit grubby in there.


This is temp fix, usually the idle control valve is dirty, throttle body, carbon deposits restrict opening etc. etc. needs cleaning.
Do check the distributer vacuum and the fuel regulator vacuum, then on to clean intake, MAF, etc and air cleaner.
These old V8' s will burn through fuel like a demon if left untreated.

If you decide not to have the throttle body heater, it's a good idea to block the open ends, just loop a hose between. The reason is, water and moisture from the air get in and corrode. You can see the rust scale in the picture. Left for a long time it can eventually corrode the throttle body from the inside.

hope this helps,