'89 Trooper: 2.8L V-6 (Chevy) / TBI / Five-speed Manual / 4WD / 277,000 miles
When I turn on my defroster, the engine idle soars up to about 2500 rpm and the defroster doesn’t work. I see that the heater unit has a vacuum actuator – probably for the defroster – so I’m guessing the problem is a vacuum leak. I’m currently replacing the vac hoses to the heater. The idle also wanders up and down occasionally and, when revved, the engine takes a while to idle down properly. Any other suggestions or ideas that I might check?