It seems to me a bit of software in the engine computer could reduce the chance of converter damage due to single cylinder misfire.
We all know there are people out there ignoring the flashing CEL, or need to limp to a safe place.
If a single cylinder misfire is detected simply cut off the fuel injector to the offending cylinder and go into open loop fuel control.
That would keep raw fuel from reaching the converter.
Still appropriate to flash the CEL I think.
Resume normal fuel delivery next time the engine is started.
With a 6 or more cylinder engine this could even be done for 2 misfiring cylinders, but not for random misfires.
I have been lucky enough to never have seen a clogged cayalytic converter, but think been through many error codes and repairs, clogged converter is the result of neglected maintenance or ignoring a cel. Now I cannot imagine a 4 cyl running on 3cyl just to protect a cat, I mean if you are on 3 of 4 cyl, you should note it is time for something!
I can see a problem with this.
I had a misfire code problem on my 3.9 Dakota for well over a year.
I’m pretty good at feeling and hearing a problem and I’ve never, ever felt that, that engine misfired.
Compression test was good. as was a leak down test.
Fuel pressure was good and even had it rigged in the cab to keep an eye on it.
New plugs, wires and distributor cap and rotor.
Misfires were on 3 & 5 so I swapped out the injectors with 2 & 4 . Still the same codes, eliminating the injectors.
New pick up coil in the distributor.
I even dropped the tank and made sure there was nothing wrong there, pump sock was clean as a whistle.
After a few days the cel would go off and about a week later it would go back on with the same codes P0300, P0303 & P0305. On for a day or two then off for a week or more.
I ran enough injector cleaner through that thing for six engines.
rigged up a can of sea foam to the vacuum line and tried clearing any deposits out that way, by letting it sit for a few hours and then fogging the neighbor hood. There were no skeeters for a few days.
Finally I misted the intake with a spray bottle of water and so far…6 weeks the light has not come on.
Had I been forced into the open loop and that those injectors were disabled, I would have been driving a puttering heap down the road for no reason.
Yosemite
A single misfire will not set a CEL, and for the light to be blinking requires the condition to be bad enough to be damaging the engine. Anybody continuing to drive a vehicle with a blinking CEL cannot be saved.
On Board Diagnostics is intended to monitor anything that might cause excess emissions and warn the driver that something has gone wrong so that he/she can bring it in and get it fixed. It is not designed to protect people from their own stupidity… and anyone who continues to drive a car with a flashing CEL is… well, you get the idea.
“A single misfire will not set a CEL”
I didn’t say that. I said a misfire on a single cylinder. There’s a difference.
“It is not designed to protect people from their own stupidity”
Modern cars are already loaded with systems to do just this already. Why not one more that doesn’t even require extra hardware?
“Now I cannot imagine a 4 cyl running on 3cyl just to protect a cat”
If there’s a consistent misfire it’s already running on 3.
“I’m pretty good at feeling and hearing a problem and I’ve never, ever felt that, that engine misfired.”
For every case like that there’s probably 50 with a real misfire.
When will I ever learn not to come to this forum with an idea that doesn’t conform to the rigid orthodoxy?
I for one, think this is an excellent idea.
Quote;
When will I ever learn not to come to this forum with an idea that doesn’t conform to the rigid orthodoxy?
I thought that you posted this @circuitsmith, because you wanted to hear other views.
I gave mine for you to take or leave. Sorry I didn’t just roll over for you and agree.
At no time in my situation did the cel flash. Maybe that is where we are differing on our thoughts.
If it is a constant misfire maybe you are right @circuitsmith . but a random misfire is something else.
I guess you are right about most people not being as atune as most of us that work on cars daily. My wife wouldn’t hear or feel if she ran over a marching band, let alone a misfire.
Yosemite
I think that is a workable idea. It would be harder to do on some cars than other depending on the system being used. Some cars sense misfire through the coil-on-plug, that would make it easier to isolate and shut down the injector.
At that point excess air would be flushed through the exhaust cooling the cat and stopping its function. THAT is not so good. So the negligent driver would wander around polluting running on 3 or 5 cylinders with the CEL on.
I could make a case that’s worse than a rich condition working over that extra fuel. A cold cat wouldn’t destroy it but we all know people who would drive around with a CEL on forever NEVER getting it fixed. Drive an SUV or truck at night and look down into the cars you are next to at lights to see how many cars have their CEL’s lit. It is astounding.
The car could just estimate the cat’s temp or estimate stress on the cat from the downside O2 sensor and just shut the engine off. Then flash a message on the DIC saying, “Enough is enough, get your car fixed dum-dum!”
If a single cylinder misfire is detected simply cut off the fuel injector to the offending cylinder and go into open loop fuel control.
That would keep raw fuel from reaching the converter.
Still appropriate to flash the CEL I think.
Resume normal fuel delivery next time the engine is started.
You’re late getting to the party. This is already being done, has been for 10+ years, except for the open loop fuel control part. Not on all cars or engines, but many.
Car sees a cylinder misfire, car turns off the injector for the remainder of the key cycle. I’ve seen a perfectly good engine computer replaced because the yo-yo working on the car saw no injector signal to cyl #2 and figured the ECM went to lunch, when the cause of the misfire was a breached head gasket and the system was functioning as designed.