Check your Constant Idle Control Motor. Takes air around the trottle body when the flap is closed and into the intake manifold to control idle speed. Sometimes they need to be lubed, BB'ers suggest a light oil. They are also known to have issues with Engine Harness breakdown and your year falls into that window. They also just fail from old age.
If you look standing on the drivers side fender at the big intake hose on the Throttle Body you will see the intake hose going to the idle motor on the left hand side. The hose to the flame trap is on the right hand side of the same big hose. The motor is mounted on a bracket that goes from the Motor Mount and a single bolt into the intake manifold. The output hose of the motor goes up through the middle of the intake manifold and connects below the small vacuum line that goes to the flame trap (it's the biggest hose on the intake manifold). Good way to check if this is an issue is to hold the gas petal down and start the engine. If you can rev the engine by pumping the gas petal, but it dies as soon as you let off the gas, likely culprit.
If you pull the bracket off to check or lube, be sure to put the motor mount bolts back in right away. Hard learned lesson just learned, mine slipped when installing an engine harness.
If the motor is bad, not all years are the same. So make sure they have the same model number. 85/87 are the same. at least pretty sure.
Good Luck,
PT
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