Engine - Camshaft Timing Slightly Off

Model Optima[MG], Rondo[UN]

Group Engine Mechanical System(12)

Number KT2007032201

Date Thursday, March 22, 2007

Area N. America

Subject
CVVT/Exhaust Sprocket/Camshaft Dowel Pin Inspection

- Description

The 2.7 L (Mu) V-6 engine offered in the Optima & Rondo platform has been designed to incorporate the use of constant variable valve timing (CVVT). The CVVT unit is installed on the intake camshaft on both rear cylinder head banks, and its design allows for control of the opening and closing of the intake valves to improve engine performance and reduce emissions. On a small number of 2.7L engines built before 9-21-2006, an under torque condition to the camshaft bolts that secure the CVVT and exhaust sprocket was recently identified. As a result of this condition the CVVT camshaft locator dowel pins and/or camshaft locator bore may become distorted & elongated. This distortion allows relative movement between the CVVT Unit or exhaust sprocket and the camshaft, throwing the cam timing off slightly. This condition generally will not produce any drivability concerns, and can at times set a very intermittent P0300 (Multiple Cylinder Misfire).

If you suspect that the valve train components might be distorted, a check of the camshaft position with the GDS and visual inspection of the valve train is required. Using GDS in current data mode, monitor the desired & actual camshaft position parameters on both engine banks. The desired value should be at 0 when the engine is idling. If the actual position is greater then + or 3.00 (fluctuating) the position of the CVVT / exhaust dowel pin and camshaft bores should be inspected. If excessive wear has been identified on the CVVT / exhaust sprocket / camshafts replace all these components together due to component wear. Tighten both the CVVT & exhaust camshaft sprocket bolt to 66.7~78.5 Nm / 49.2~57.9 lb-ft while maintaining the stationary position of the camshaft by holding the hexagon portion of the camshaft. Failure to properly inspect valve train components and/or torque the intake and exhaust camshaft bolts can cause wear and repeat dowel pin & bore distortion.