Your very likely to have oil in the ECU. Some open the ecu up to clean it, i prefer not to and have used the following method several times on different Disco's
very easy diy job.
Remove the ECU . Spray lots of contact cleaner into the red ecu plug and allow it to seep inside the ecu to flush it out. then stand it on end to allow it to drain and dry while you replace the injector harness.
Remove the rocker cover and the harness just runs over the top of the injectors,the harness has 5 plugs each one just clips onto each injector. remover each one and the small bolt holding the harness plug in place at the front of the engine. then clean each injector plug and the main harness plug at the front .
Replacement of the new harness is just a reversal as they say.
Oil will continue to drain out of the engine harness over the next few months, just clean the ecu red plug every now and then until it dries up.
Sorry if this a teaching you to suck eggs response
