How could hundreds of clearings of the OBD codes cause the catalytic I/M readiness monitor to set?...

[Michael]

On Mon, 24 Apr 2023 14:10:13 +1000, Xeno wrote:

Does the PCM shut down the spark or the fuel to that misfiring cylinder?

It will definitely shut off the fuel - if nothing else. If you have fuel
but no spark you will be flooding the cat with raw fuel. That\'s bad.

I wonder what it does because it\'s impossible to shut off the fuel since
there is only one intake manifold and the injectors inject fuel into it
just like a carburetor would have, only a bit closer to the cylinders.

If they shut down the fuel there will ALWAYS be fuel getting into the
cylinders, but maybe the baffles are designed that one injector \"mostly\"
injects into one cylinder for cars that aren\'t direct injected (which is
most cars that are NOT direct fuel injected).
--
[I filter out Google Groups posts so if I don\'t reply, that may be why.]

 

[Xeno]

On 24/4/2023 2:24 pm, Michael wrote:

On Mon, 24 Apr 2023 14:10:13 +1000, Xeno wrote:

Does the PCM shut down the spark or the fuel to that misfiring cylinder?

It will definitely shut off the fuel - if nothing else. If you have fuel
but no spark you will be flooding the cat with raw fuel. That\'s bad.

I wonder what it does because it\'s impossible to shut off the fuel since
there is only one intake manifold and the injectors inject fuel into it
just like a carburetor would have, only a bit closer to the cylinders.

If they shut down the fuel there will ALWAYS be fuel getting into the
cylinders, but maybe the baffles are designed that one injector \"mostly\"
injects into one cylinder for cars that aren\'t direct injected (which is
most cars that are NOT direct fuel injected).

Should mention, I suppose, that it only apples to sequential injection
with cylinder specific misfire monitors, V8 & V6 engines typically. Gang
fired injection systems just might not run so well with *half* the
cylinders getting no injection pulses. 😉
For the rest it\'s goodbye to the cat if the vehicle continues to be
driven, or it goes into some form of severe limp mode and that pretty
much forces rectification of the issue.

--
Xeno


Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)

 

[Scott Dorsey]

Xeno <xenolith@optusnet.com.au> wrote:

On 24/4/2023 5:09 am, Michael wrote:
On Sun, 23 Apr 2023 23:00:56 +0530, mike wrote:

You don\'t seem to know engines well, so allow me to explain that when the
engine sees a misfire in 1 out of 200 revolutions (most cars), the engine
control module permanently shuts down the spark to that cylinder (to
protect the cat).

Does the PCM shut down the spark or the fuel to that misfiring cylinder?

It will definitely shut off the fuel - if nothing else. If you have fuel
but no spark you will be flooding the cat with raw fuel. That\'s bad.

It\'s bad in the sense that it will burn up the converter but... that might
be an advantage if you have a gunked-up converter. At least if it doesn\'t
explode.
--scott
--
\"C\'est un Nagra. C\'est suisse, et tres, tres precis.\"

 

[Peter W.]

Why does this entire exchange remind me of Jimmy Neutron and its BMW?
Fundamental lack of understanding, and a closed mind.

 

[Frank]

On Mon, 24 Apr 2023 14:42:13 +1000, Xeno wrote:

For the rest it\'s goodbye to the cat if the vehicle continues to be
driven, or it goes into some form of severe limp mode and that pretty
much forces rectification of the issue.

I was also wondering how the fuel could be shut off to any cylinder since
very few normal passenger car engines inject into the cylinder itself.

 

[Bob F]

On 4/25/2023 10:01 PM, Frank wrote:

On Mon, 24 Apr 2023 14:42:13 +1000, Xeno wrote:

For the rest it\'s goodbye to the cat if the vehicle continues to be
driven, or it goes into some form of severe limp mode and that pretty
much forces rectification of the issue.

I was also wondering how the fuel could be shut off to any cylinder
since very few normal passenger car engines inject into the cylinder
itself.

My sienna has one injector for each cylinder. Why would that be?

 

[Scott Dorsey]

In article <u2ac2l$18mda$1@dont-email.me>, Bob F <bobnospam@gmail.com> wrote:

On 4/25/2023 10:01 PM, Frank wrote:
On Mon, 24 Apr 2023 14:42:13 +1000, Xeno wrote:

For the rest it\'s goodbye to the cat if the vehicle continues to be
driven, or it goes into some form of severe limp mode and that pretty
much forces rectification of the issue.

I was also wondering how the fuel could be shut off to any cylinder
since very few normal passenger car engines inject into the cylinder
itself.

My sienna has one injector for each cylinder. Why would that be?

Your Sienna is injecting into the intake of each cylinder, so the computer
has fairly independent control over cylinders. But there is still a
very tiny amount of mixing in the manifold.

Cars that have direct injection (which include a lot of newer BMWs) inject
directly into the cylinder rather than the intake. This requires much more
rugged injectors and much more expensive ones.
--scott

--
\"C\'est un Nagra. C\'est suisse, et tres, tres precis.\"

 

[Xeno]

Bob F <bobnospam@gmail.com> wrote:

On 4/25/2023 10:01 PM, Frank wrote:
On Mon, 24 Apr 2023 14:42:13 +1000, Xeno wrote:

For the rest it\'s goodbye to the cat if the vehicle continues to be
driven, or it goes into some form of severe limp mode and that pretty
much forces rectification of the issue.

I was also wondering how the fuel could be shut off to any cylinder
since very few normal passenger car engines inject into the cylinder
itself.

My sienna has one injector for each cylinder. Why would that be?


More accurate fuel distribution between cylinders.

____
Xeno

 

[Hiram T Schwantz]

On Sun, 23 Apr 2023 23:00:56 +0530, mike posted for all of us to digest...

The question isn\'t about how horrible a person I am

Sni9pped for your pleasure!

Is that you Arlen?

--
Hiram