So I have been looking for this vacuum leak for a while now.

MOST REVEALING - Listening to the Air intake with a small peice of tube, I can hear a gentle hissing, like normal then after about a minute A tattering or tapping begins really loud and that goes on for about two minutes, then A big surge in idle, then the tapping goes away and the idle drops down, then the process repeats itself almost like clockwork.

Idle air control valve? replaced couple years ago.

Sticking throttle plate?


ALSO, I clamped off the brake booster hose but that did not increase idle speed,
(I thought it would if the brake booster were bad?) but when i pump the brakes the idle increases then goes back to normal?

I found A leak at the new PVC valve, listening through a small peice of tubing, Clearly hissing so I tracked it down to where the metal and the plastic are crimped together, installed the original Motorcraft one and hissing is gone, Still rattles like mad.

Found the crankshaft ventilation filter caked with oil. replaced it with a new one.
Air filter looked really clean.

Thanks.

 

Where is this filter located? I've not seen it mentioned in my '94 service literature. Maybe is has a different name?

 

On mine (5.8) it is under the air filter on the right side of the box.

There is a clip that holds it on to the air box on the outside of the box, pull that off and pull off the hose attached to it (right by the clip) and the filter will come out.