A rough idle can often be traced to a loose or damaged Intake Engine Variable Valve Timing Fastening Bolt, because the actuator may drift on the camshaft nose and alter valve timing unpredictably. Technicians should first scan for P0011 or P0014 codes; if present, remove the valve cover and inspect the Intake Engine Variable Valve Timing Fastening Bolt head for witness marks indicating rotation. A sheared Intake Engine Variable Valve Timing Fastening Bolt will show shiny metal where the hex has spun against the actuator, and magnetic debris may cling to the surrounding area. Remove the central plug on the VVT solenoid and insert a pick to feel whether the Intake Engine Variable Valve Timing Fastening Bolt is still tight; any radial play suggests replacement is mandatory. If the Intake Engine Variable Valve Timing Fastening Bolt has backed out partially, check the camshaft keyway for fretting that can prevent proper re-torque. Clean the threads with brake cleaner and compressed air, then chase them with the correct tap so the new Intake Engine Variable Valve Timing Fastening Bolt achieves full engagement. Lubricate the underhead of the replacement Intake Engine Variable Valve Timing Fastening Bolt with a thin coat of engine oil to reduce friction during tightening, but avoid oil on the first three threads so the thread-locker can cure correctly. Torque in two stages: first to 20 lb-ft, then to the final angle-specified value while holding the camshaft with a holding tool so the Intake Engine Variable Valve Timing Fastening Bolt does not simply spin the camshaft. After repair, clear the codes and run the engine through a cold-start cycle; if rough idle persists, verify that the Intake Engine Variable Valve Timing Fastening Bolt is not bottoming out due to an incorrect washer thickness. Document the repair order with photos of the removed Intake Engine Variable Valve Timing Fastening Bolt to protect against future warranty claims. By systematically addressing the Intake Engine Variable Valve Timing Fastening Bolt, drivability can be restored in less than an hour.