1990 Geo Tracker Engine idles irregularly

You have a vacuum hose connect to the intake manifold. This is broke because of heat. Replace the hose from the intake manifold to the front VSV. Repair cost about 2 dollars if you do it your self

By the way before you put a new vacuum hose on be sure you clean the pilot hole out. It's very small and is as small as gas jets on a furnace but believe me there is a hole there but very small. I used a bristle from a wire brush I had to clean the hole out. If you don't and just replace the hose and the hole is blocked your car will still idle high. This also supplies all the vacuum for distributor advance EGR valve and idle up valve and the idle up switch is why your engine is idling hi about 1500 rps. No vacuum nothing works right but you don't get any idiot light not even computer codes.