Land Rover Repair: Land Rover Disco 1998 - Smoke on the water!, land rover discovery, smog test

Question
Q: land rover has a wondering idle. sometimes dips well below 500 to the point it feels like it will stall. also has a rough idle some times.

Q: having trouble starting. running platinum plugs. takes time to start when sitting for a bit.

Q: exhaust smell and poor smog test results. some times see a bit of smoke then it dissapears but still smells strong. it was flooding due to a poor ECM but that is changed now. pipe is black at the tip.

any help would be great.

1998 land rover discovery 1 4.0L


Answer
Your symptoms do not point to any single problem.  The starting may be a result of losing fuel system pressure.  You'd have to put a gauge on it and see if the pressure holds after shutting the truck off.

If it loses pressure it's either leaking out the injectors into the motor, or leaking back through the pump check valve or pressure regulator into the tank.

As to the other . . . I would find a shop with the proper LR test system and run it while watching the live data screen.  That's the fastest way to get to the bottom of something like this.  Otherwise you are just guessing, as tests of components when the engine is off won't often show problems when running.

Tail pipe ends are always black.