Hello all .
I have a 3.5 injected old 89model . I was checking vac advance function and have discovered my take off fitting for the vac adv tube on the plennum must be blocked in some way . Does anyone know if this little metal fitting on the top of the plenum which the tube plugs onto has a ball and spring or anything in it . I poke a wire into it and it seems blocked solid . At idle or reving slightly there is no air at all drawing into the manifold through the fitting with the hose disconnected .
Thanks Mark

It's a plain fitting which experiences manifold vacuum only when the throttle blade is moved slightly open. The hole into the space by the throttle blade is quite small, less than 1mm. Personally, I cheat, and use a 1.5mm bit and drill the sucker out. You can also extract the nipple, its a push fit. Some carby cleaner applied with a thin nozzle may also clear it.

thanks Bee Utey .
By plain fitting do you mean its simply a strait open tube into the throttle body . No obstructions !
Is the nipple seated in the alloy casting of the throttle body and theres a hole less than 1mm in the casting . The hole in the nipple seems larger then 1mm .
Can I simply drill down through the nipple into the alloy at the existing internal diameter of the nipple maybe with some grease on the drill bit to collect the drill shavings ?
Cheers

Plain yes, as in there's nothing but a hole. The throttle blade passes the hole as it opens. The fitting sits in a socket which is much smaller to the manifold. If you have a tiny drill bit which reaches through the fitting then OK. Otherwise just yank the fitting with pliers. The shavings fall down the front face of the throttle blade. Just remove the intake hose, stuff a rag in the throttle cavity, and collect the shavings.

The mystery is solved thankyou