I just purchased a FSM (Field Service Manual/downloaded online from eBay) and this is all I can find out about the timing on an S-Type. If you would like a copy of the manual, I would be more than happy to send it to you as an attachment if allowed. Email me..
[email protected]. My name is Jan, retired, and tired of the problems my 2001 Jag S-Type 4.0 is giving me, but still love it.
Variable Valve Timing (VVT)The variable valve timing system improves both low speed and high speed engine performance, engine idle quality andexhaust emissions. It is an infinitely variable system operating on the intake camshafts only. There is the equivalent of
48? ofcrankshaft movement between the retarded and advanced positions. Engine oil pressure operates the system under thecontrol of the ECM.For each intake camshaft there is a valve timing unit, a bush carrier assembly and a VVT solenoid.The valve timing unit turns the intake camshaft in relation to the primary chain to advance and retard the timing.The unit consists of a body and sprocket assembly separated from an inner sleeve by a ring piston and two ring gears; theinner sleeve is bolted to the camshaft.The ring gears engage in opposing helical splines on both the body and sprocket assembly and the inner sleeve, to transmitdrive from the assembly to the inner sleeve.Engine oil pressure moves the ring gears and piston to turn the inner sleeve in the advanced timing direction and a returnspring reverses the direction for retard.Additional springs absorb rotational and axial backlash to reduce noise and wear.
Variable Valve Timing (VVT) SolenoidThe valve timing solenoid controls the position of the shuttlevalve in the bush carrier. A plunger on the solenoid extends when the solenoid is energized and retracts when the solenoid is de-energized.With the vehicle stationary and the engine compartment open, operation of the valve timing solenoids may be audible when the
lubrication pulse occurs at engine idle speed.
