Idle Vibration or Misfire
Check Engine Light Step 2 - An engine tune up is necessary for proper operation and should be performed according to manufacturer's recommendations.
Vacuum Leak Step 4 - An engine depends on an equal amounts of compression in each cylinder to run smoothly. If poor compression exists in one or more cylinders it can cause rough idle. To check for this condition perform an engine compression test to compare readings. Once a low cylinder has been detected an internal engine inspection is required.
Compression Test Step 5 - An intake valve must seal completely or intake gases will contaminate the intake charge of other cylinders causing the engine to idle rough, to test this condition a leak down test must be performed. If positive results are produced for leakage, a valve job must be performed.
Intake Valve Cutaway