I have noticed that when I go through mud, raining hard driving, or pressure wash underneath, that the engine will start to stumble at idle. no codes are thrown. acceleration is fine and it will not cut off, just rough idle. it has new plugs and wires, and i went all around the engine with a spray bottle trying to see if I could pinpoint the issue. any ideas where to go from here?

 

DI or DII?

 

What kind of wires? Every time there is moisture in the air my Disco runs terribly, misfires the whole nine until the engine compartment heats up and dries. I replaced the spark plugs and that half solved the problem. I am changing to Magnecor 8mm ignition wires. If you did not install Magnecors then you may want to they seem to be the only wires recommended around here.

 

they are 7mm wires. not magnacore. it is a disco 1.

 

I would have to say that it is your plug wires.
What brand are they?
How long have they been on the truck? (Time and miles)

 

they are duralast wires. it did this since i have had it with sti 8mm wires.

 

Well when I bought my truck 2 years ago I used Duralast wires, they lasted exactly one year. (20,000 miles)
Went bad, replaced under warranty, 3 months later bad again, replaced under warranty, 3 months...bad.
I know have Kingsbourne plug wires, 8mm and so far so good but it has only been a few months so unless you are on a really tight budget I cannot recommend them yet.
They were $35.
Because it is running bad when wet that tells me that it is most likely the plug wires shorting out when wet.
It could also be water inside the ECU.

 

well this has happened with two ecu's, it has a new one in it, and it is dry. i loaded down the plug wires with water and nothing happened. plus when it rains, water isnt accumilating on the plug wires on the engine. could the crank sensor be an issue?

 

Yes it could be the crank sensor.
If it were a DII I was going to suggest that but on DI's they are not as trouble prone.

Things dont have to be "wet" just the excess moisture in the air can cause these types of problems.

 

well it definitely requires it to be SOAKED for it to happen. Like a heavy splash through mud, or driving through heavy rain, or pressure washing underneath the vehicle