Vacuum Leak Test
Vacuum Leak Step 2 - Vacuum lines can become hard due to under hood temperatures which produce an unwanted vacuum leak.
Broken Vacuum Line
Replacement Vacuum Line Step 4 - If after inspection, no broken vacuum lines are found carburetor cleaner can be used to further inspect for leaks.
Carburetor Cleaner Step 5 - After starting the engine and allowing it to idle, spray the cleaner near and around the throttle bore gasket, if the gasket has failed the engine will react to the spray by increasing the engine idle speed as the cleaner is burned. If the engine is idling rough it will temporarily smooth out as the cleaner is consumed.
Checking Throttle Bore Gasket