Check for disconnected hoses and the like....sound of hissing anywhere ?

Rap the idle valve with a screwdriver handle. (Alloy can with a rubber strap holding it down, just right of center, front of engine looking from radiator).

Turn ignition off...disconnect idle valve from loom...restart motor.
Any change ? If yes....Idle valve faulty.
If no....possible idle controller faulty or not powered.

Check OVPR up above the relay box,( I seem to remember, in passenger kick panel.....someone confirm ?..).......has a fuse in the top..10amp.

Replace if blown...check date on OVPR...if 2000yr or earlier...replace .

Other possibilities are stuck distributor weights.
Jambed/misadjusted throttle linkage.
Return spring to throttle missing/broken.

Constant vacumm to advance side of distributor.

.

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