engine surges at idle but runs fine under load on 1990 Honda Civic

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I changed out the fuel filter, but the engine will surge up and down when at idle. at times almost feeling like it is gonna die but not accelerating more than about 1500 rpm. Would this be a vaccum or electrical issue or something totally different?
(2) Answers
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The 1500cc engine uses throttle body injection, check the coolant level first if the coolant level is low the engine will surge, check for vacuum leaks around the intake manifold. Valve clearance on these engines are frequently over looked as part of a tune up, they are mechanically adjusted. Check the grounds of any wires around the intake or thermostat housing.
The Idle Air Control is to blame. The Honda civic's "IAC" goes bad and leaves the valve open so that the car can still run. its kinda a failsafe but its annoying. Its located on the back of the intake manifold good luck.