Bad Cats?

Would the following be indicative symptoms of bad catalytic converters:

1. Rattle, like marbles, in the cats.
2. Turn red from heat.
3. Smell bad.
4. Defender runs very poorly at low RPM's.

I know the first 3 are givens but if the cats are bad will if affect the engine function at low to mid RPM? Sorry if that is a sill question.

They are dead. Yes as they get blocked up they will cause the truck to run very poorly, replace them now.

So it was not the cats but a bad ignition module.....running poorly and dumping fuel into the cats apparently makes them turn red hot. All fixed no though!

I had the same thing happen on a Subaru... the ignition module's death allowed a lot of fuel to be pumped through into the exhaust.

Once you've had that much gas in the cats, though, they'll die soon, although the original culprit was the module. So, plan on a replacement before long...

Head gasket failure will also knacker your cats.