glowing red hot cat

Possibly the cat is broke and the core lodged in sideways. I have a couple here that did that

 

Fuel mixture is way off and the Cat is having to burn all the excess Fuel to keep emissions down.

Or it could be a bad cat.

 

Is it firing on all cylinders?

 

If the fuel mixture was off, wouldn't both cats be red?

 

Not necessarily. Each bank operates independently.

One or two dead cylinders could put enough fuel in a cat to heat things up.

 

Check to see of plugs are fouled and not firing. Had this happen a few years ago and it was a bad plug.

 

Agree with this. Had this on my 360. Not firing on 1 or 2 cylinders, spent fuel went into cat and burned there. Don't drive too much on it, it'll trash the cat. Pull the plugs and check visually for changes in ash color. The ones that don't match are probably bad/ignition wires/coils bad.

 

Ah, I see, that makes sense.

 

Is it.....this cat by any chance?
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Bet you've been holding on to that photo for just the right opportunity, eh Schaf? Priceless...

 

Not an F car but, last time I had a cat glowing red hot, it's because the valve timing was off.

 

How are the headers on that bank? Failing headers will trick the ECU via O2 sensor reading to dump fuel into that bank. That would kill your motor and cat.

 

I had to do it....

 

Pity!

 

I had the exact same thing happened to me on my previous 355. The car drove fantastic all night and all of sudden, the SDL came on and I drove the car home in limp mode. When I got to the garage, I can see my passenger side Cats glowing through the engine bay. Took it to the dealer and it turns out that my cats were old and clogged.

 

Bad spark plug wire is a strong possibility.

 

When on the highway, how low does your coolant temps go? If your coolant goes below 11:00 o'clock (180°F or 82°C is normal thermostat opening) after full warm up, it means your thermostat is 'stuck open' (normal fail position). This causes 2 problems, the first is your ECU will think your engine is cool and will richen the mixture. The second is the coolant is rushing through the engine, which does not allow the coolant enough time to draw sufficient heat away from the engine.

Sooo, your engine will actually be hotter than the coolant temp gauge shows. Then because of the lower coolant temps the ECU will administer extra fuel as if the engine were cool ...... causing the rich A/F ratio, leaving that extra fuel to burn in the cats, overheating them.

Note: The ECU coolant temp sensor and the temp gauge sender are only inches apart in the same coolant path. So what ever your gauge reads, so does the ECU.

+1 ......

+1 ....

 

i like this idea. 1996 355 obd2 car i assume? 15 y/o with low miles is as bad as high miles. cat substrate breaks down and plugs = heat. Since car is obd2 if the other theories presented make sense then you would see 0300 series codes for misfire. your sdl are probably working and have been telegraphing the problem for quite some time. It is starting to get critical. put a gage on the exhaust and see what the back pressures are. Increase pressure on the right where you got the red cat = cat death time to replace. If you get sdl's and p0300 series codes at the same time then I'd start looking at plug wires, injectors etc...

 

You beat me to it. I was about to post that a misfire should throw a P030x code.

 

I lost a cat due to 3 intermittent spark plug wires.

The cat glowed and the substrate subsequently failed
When I tested (you will need a multitester from your local auto parts store....around $20-50 bucks depending on features but any one will do) all the spark plug wires for resistance....I found the readings very consistent, however when I subsequently tested for continuity (while lightly twisting and bending the wires) 3 of the plug wires showed no continuity.

Replaced all the spark plug wires and no issue since.
This is a very common problem on 355's .
The design of the spark plug wire routing is very pleasing to the eye however very poor in design in that the spark wires are crammed into the valve covers.

 

Do you have the stock ceramic cats or aftermarket metallic cats?

If stock ceramic cats......take a rubber mallet and tap the cats.....if they have failed you should be able to hear a rattling sound as you tap the body of the cat.

 

Glad to hear.

Sometimes it really is the simple thing.