A car with a vacuum hose night mare like that year Honda which used to only idle at 1,800 cold. I would look first for cracked or split vacuum hoses near where the most heat is. Then use carb cleaner when the engine is hot to help locate the air leak into the intake tract. Spray cleaner onto the gasket surfaces intake manifold to cyl. head If idle speed gos up there is a leak! keep trying until you find the biggest speed change the largest leak. Just a quick way to find vacuum leaks. Idle air anti backfire valve between the air filter and intake is also what I would look at. Start the engine cold and locate inside the air filter under the top the 1/2 inch 13mm tube and plug it with your finger if idle returns to normal the anti backfire valve is leaking.