New car

The reason 'pre-ecu' cars with carbs ran better was somewhat simpler.

Air/fuel ratio is critical. Too rich and you waste fuel, harm the environment, and have poorer performance. Too weak and you risk engine damage.

Carbs were not able to cope with differing climatic conditions, so it made sense to always run them a bit too rich, rather than risk a holed piston.

When climatic conditions were such that the air was dense and laden with moisture, each 'breath' of the engine took in more oxygen, so the air/ fuel ratio was nearer to ideal. This is why old cars ran better in the rain.

(For racing purposes, carb jetting was set for things like altitude and climatic conditions. This was a black art; the basic rule was 'in the wet, jet up'. One well-known motorcycle tuner of the sixties had a sophisticated barometer in his van, and a carefully-guarded hand-written table of optimum settings for each of his engines.)

Chris

Not quite sure why a loom would need replacing after being submerged in water?

Maybe just because the attached connectors are corroded. Any repair such as described always has potential/likely to become a nightmare, so it may also be a bit of arse covering/way to avoid the job.

Because it's cheaper, easier, and quicker than replacing all the corroded multiplugs, always assuming the corrosion hasn't passed from the plugs up the cables a bit. And, of course, always assuming there's no damage from shorting.

In a way, it's academic. The car's f***ed.

I would have thought the wiring loom was the most robust of items in a car when submerged in water. perhaps the clue to this story is the word "dealership"!

I had a 2004 S-Type Jag in 2008. There was an umpteen pole connector just inside the front grill that had already suffered water ingress and rotted out the first few mm of copper of one or two of the connections.

So, while I'm with Dave on thinking a bit of light dunking ought to be fine, I can certainly see an argument for mass loom replacement!

Right. I was just thinking a car submerged in water might have more pressing problems than the wiring loom.

Quite. Most connectors these days are moisture proof and grease filled. The wiring itself unlikely to be damaged. Or rather if it was I'd expect lots of other things to be beyond saving too.

I do know that at one time a small fleet of new camper vans were declared right offs after their noses got in deep water, presumably sea water. Even though they were not submerged it just wasn't worth clean up because of possible later claims. Same as any fire in a car, automatic right off, just in case of later claims.

Last new car I bought was a Fiat Croma CHT 1987. The car was blessed with a rattle from somewhere deep down in the front fascia. Presumably a hidden screw or something. Took it back to the deater, all they could do was spraying the fasia with some oily substance, presumably to dampen the noise? To add insult to the injury, the dealer dented the car and wouldn't admit to it. Oh, and the dealer lost the service book during re-building work, but found it again several weeks later. The ratlle was ever there for the next 10 years. During that time, the speedo stopped working, the alternater blew, the head gasket blew, the basic plastic fascia warped from sunlight. However, the Type 4 design, big car FWD, was quite modern at the time.

Only if they are water tight most looms are not, connector blocks get wet and the terminals corrode.

May be those in the engine bay or beneath the vehicle, connectors within the interior of the vehicle or behind the dash wont be unless the vehicle is specifically designed for off road use.

Are you really saying the wiring loom would be damaged by water before the rest of the car - like the interior? Or engine, come to that.

It depends how deep it's been, unless it's really submerged then the engine's unlikely to care, changing the carpet's far cheaper than changing the loom.