110 Defender TD5 stuttered in the rain

How do peeps,
I was on a long drive from home near Oxford up to Loch Ness. I was about 7 or so hours in, no bother whatsoever. Cruising at Motorway speeds as I have so many miles this Morning.

Close to Glasgow it started to rain. It was heavy enough for me to drop back a little on the speed and concentrate a little harder. As it came down the lights and wipers went on. The radio and heater blower was already on.
After a few miles of sitting in the mist of the car in front, it stuttered, not just a single misfire or two but what seemed like a momentary power loss. Only for a split second.
Then again a few seconds later. I slowed down to about 50 or 60 and I seemed to get less frequent.
Back on the power and up to cruising again, it's still raining and the it is again. 3 or 4 stutters, not a single cylinder misfire, a total momentary power loss.
It's not a long enough stutter to cause the car to slow really but I can feel it.

I pulled over for a bit and it's sat there idling fine. Gave it a rev, fine.....Hmmm.
I then switched off all the unrequited electrical consumers and carried on but it was still there. I carried on hoping to make it all the way and planning a stop at the next services to have a proper look.

Then the rain stopped, the road cleared and no more stutter. It's totally gone. I put all the electrical consumers back on, still fine. In fact it went the next 3 hours, in the dry with NO bother.

So, what was getting sprayed, wet, soaked that caused this?
Something in the engine bay? Must be surely.
Has anyone else had this?

Just check the ECU isn't getting wet... mine totally died, and after much money left my account I had a new ECU, due to water ingress... they didn't solve the cause - the seal around the centre seat inspection panel was rotten and water was getting into the ECU compartment, and that was from surface water, not deep wading!
I've also heard that there is a connector near the heater box somewhere that is vulnerable to water ingress, possibly due to water coming up off the road wheel.

I have considered Gwyn Lewis mud shields and possibly relocating the ECU... but seem to be tied up with just keeping it serviced and addressing faults as they arise...maybe one day I will manage to save some money

Thank you, I've just had a look and the box under the drivers seat is bone dry and there's no sign of any staining from water in there or on the ECU.
I've checked the wiring up near the heater box but having driven and let that car sit it's all dry in the engine bay now. I've covered the connector block up with a plastic bag so we'll see what it's like on the way back.

There are also some connector blocks on the other side, close to the expansion tank so I'll cover those too.
I hope it's OK on the way back.

Had the same thing on my 110 TD5. I finally concluded that it was water in the airbox, although the tide mark in there was a bit of a give away. Anyway no more trouble having fitted a snorkel and no more tide marks

I thought it had something to do with the rain, didn't think it would result in needing a snorkel!

Got any recommendations?
I suppose in reality it's just a tube with an intake on top and it's down to asthetics and personal choice.

The water was getting in there through the ill fitting pipe work between the wing grill and the airbox. I would guess that if you sealed all the joints, as others on here have, you'll be ok. The original pipe work is of a stunningly low quality, poor fitting joints - thin flexible plastic, that I would guess will prove to be hard to seal. Just seemed a better solution to me to fit a snorkle and replace all the pipe work up to the airbox at the same time. Gave my missus something to buy me for christmas too.
More than half way to christmas now, overdrive this year...

One I used on the link...

https://www.landyzone.co.uk/posts/3340871/