355 One Cat is glowing red but no SDL on

Guys,

I found out one of my cat was red after 40 mins driving.
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No light goes on.
Any idea ?


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Is the cat ecu connected or bypassed? Is check that first. But generally too much fuel getting in the cat and then being burned there or the cat is clogged. Pull it and do a visual inspection.

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Well, for one, your CAT temp warning system isn't working. And two, looks like that bank must be running really rich or have a cylinder or two out. Three, if a metal core cat it's probably toast.

 

The exhaust glowing red doues not necessarily mean that you were in the SDL trigger zone. I don't know how red the exhaust has to get to trigger the SDL but, when I bench tested a known good 348 thermocouple, I had to heat-up its probe (with a small torch) to bright red/orange in order to bring its output to close to the SDL trigger point.

I would first investigate why only one side is getting red. Perhaps collapsed cat internals causing some restriction to the exhaust flow?

 

On a 355 (I think this is your car), a red hot cat is a bad sign. You have excess fuel in the cat, even if it has not yet triggered a SDL or a CEL, you need to sort that out before it becomes a fire hazard.

 

Thanks for the information. So what should I do to locate the problem ?

I didn’t feel that I was losing power though.




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Have you modified anything on the exhaust system? e.g. O2 extenders with cat material to fool the O2 sensors, dummy plugs on the Slow Down (thermocouple) ECUs, etc? I don't see how the car is not detecting a problem with either fuel/combustion problems or cat temperatures.

Looks like you have a F355 2.7 car?

 

Glowing red cats mean loose connections check and make sure you're O2 censors are connected tight

 

1) physical inspection, 02 car ecu etc
2) pull the cat and look inside for damage/blockage
3) figure out why it's getting fuel (stick injector, bad fpr, bad plugs) are few easy low cost possibilities.

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Make sure that you car isn't running too cool. If it is the ecu mapping won't get out of secondary enrichment = extra fuel in the system. Also make sure that your coolant temp sensors are in good shape and sending the correct temp signal.

 

btw this is why I witched to the 355 fan switch, the 348 switch runs 5 degrees cooler or so with some manufacturing variance..

 

Both of the header and cat are aftermarket. Changed by previous owner.
My car is a 2.7 version.


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This happened after I had 40 mins hard drive. So the car wasn’t running cool.
Coolant temp has been changed 2 years ago. It seems working fine.


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Which coolant temperature sensor? There are 3. One for each Motronics ECU/bank and one for the gauge.

https://www.ricambiamerica.com/car-diagrams/ferrari/v6-v8/355-group/f355-m2-7-1995/water-pump-and-oil-water-heat-exchanger.html

The ECUs may not exchange temperature information, so maybe one sensor is causing one bank to think the engine is still cold? I stand to be corrected

 

Might I suggest a heat gun and measure the temperatures of he banks of header pipes and cats at similar spots to check if there are any real differences between banks and or points in the exhaust system. The colour red is not necessarily a tell tale indicator after a hard run and low light conditions which will make it look brighter than a cat in brighter lighting.

 

You coolant temperature sensor my be just fine.
However.
That doesn’t mean your thermostat hasn’t failed.
Have a read of this thread to understand more about what I am describing.
https://www.ferrarichat.com/forum/threads/355-owners-only-more-data-samples-needed-anonymous-poll.377706/

 

Is it running smooth? Unburned fuel is ending up in the cat or the cat is clogged.

 

OR......................

 

He has a failed header.

 

If you still have the secondary air injection system fitted check for leaks, failed check-valves, cracks in the tubes, loose connectors, stuck open vacuum valves etc.

Excess air getting in upstream of the cat can cause overheating catalyst (as well as a cracked manifold, as mentioned above or damaged manifold gasket/loose nuts & so on).

I am personally convinced that a few of the 355s that have gone up in flames have been due to failed secondary air system (although most went to the well documented fuel leaks)

 

The air pump is still working whenever cold starts. It run for few mins and stopped. How could it affect the cat when the pump is stopped ?

Thanks


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What he means is "when there is a air leak close to the upstream o2 sensor, the sensor will read a lean condition where none exists and the computer will richen the mixture during the next combustion cycle. The over rich mixture does not burn completely and ends up burning inside the hot Cat converter, thereby melting the inside of the converter". I have seen it many times.

 

Hi Joe,

We had a Chevette (remember them?). My wife was driving it from Crockett, Texas to Houston about sundown. She called me to say that every time she tried to turn the lights on, the engine would die. Later, a local shop diagnosed it as a bad battery and replaced the battery. I went to drive it that night and it wouldn’t start. I roll started it and tried to drive it back to proper functionality. The engine would not run faster than idle. I drove to a local strip mall parking and lot and drove around in circles. After a few minutes of this, a guy drove over to me and said that there was something glowing under the car! It was the catalytic converter. After a second visit to an auto shop, it was discovered that the alternator was not recharging the battery. When the battery got down to a certain level of charge, there was insufficient electrical current to give a proper spark. Even at full throttle, the engine would not turn more than about 1200 rpm, so any excess gas would go out the exhaust ports and into the catalytic converter where the catalyst would attempt to clean the excess fuel by burning it in the converter and wind up just over-heating it until it glowed. Replacing the diodes in the alternator corrected the problem.

How well does your car start and run? If my 430 battery had a voltage that was too low (10-11 volts), the starting process sounded quite odd and lacked any alacrity. You might have the battery and alternator checked.


Tom

 

It may be helpful to check the long and short term fuel trim numbers with a scanner.

 

Ironically, modern cars actually do a variation of what you describe on purpose in order to get the cats up to working temperature. The strategy is called ‘cold start spark retard’. The spark is retarded and with the richer fuelling for start-up combustion continues in the exhaust manifold. It gets the cats up to working temperature faster and is why cars no longer have secondary air injection.