My 1999 td5 land rover has a missfire from number 5. Iv replaced number 5 injector and the injector harness and iv cleaned out the ecu plugs. The egr valve has been replaced with a kit. The oil is ok and the header tank is not pressurising and no coolant loss. Starts ok smoke from exhaust and missfire on tick over fills the street with smoke when driven down road and carrys on misfiring

SOURCE: land rover discovery td5 oil in coolant

Might be a blown head gasket. take it for a compression test.

SOURCE: how to adjust rocker shaft on discovery td5

There are adjustment screws on the rockets according to RAVE.
The procedure is as follows:
1) Rotate the engine clockwise until No 1 injector lobe is at full lift.
2) Rotate rocker adjusting screw clockwise until the injector plunger is felt to bottom out.
3) Rotate rocket adjusting screw anti-clockwise one complete turn to give plunger the required bump clearance and tighten rocker arm adjusting screw locknut to 16Nm. Ensure the screw does not turn as the locknut is tightened.
4) Carry out the procedure for the remaining 4 rocker arms.
5) After completion of rocker arm adjustment slowly rotate engine clockwise 2 complete turns by hand to ensure that no injectors are bottoming out on their plungers.

SOURCE: Land Rover Discovery TD5 1999. Where is the Fuel Relay Switch

In the engine fuse box under the bonnet ,relay is the closest one to the front of the vehicle ,about £7 to replkace