I've always frequented these forums looking for interesting things about the Land Rover world. As an owner of a 2002 D2, I had a question that I'm hoping some of you guys could answer. Whenever its rather humid or after a long heavy rain, I get extremely poor performance; almost a sort of missing around 2000 rpm. It also struggles to get up to speed and it seems like it has to "dry out". The service engine light is nearly always on but in this case, it's often flashing. This also happens when taking it off road and going through bigger puddles or crossings. I've read that it could be bad spark plug wires or something of the sort with water mixing in where it doesn't need to be. The Discovery is just a standard SD V8.

 

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engine light flashing equals misfires
you need a good maintenance like plugs 8 mm wires plugs and coils. Coils are found pretty cheap at rock auto same with o2 sensors

but you want to check your wiring and connectors
to o2 sensors
but usually rain and humidity can escalate problems if your coil packs are in bad shape