GM, misfire code: how do they detect this?

My brother's Safari failed the NYS inspection due to engine codes -
specifically, "#6 cylinder misfiring." I'm curious as to how they
detect this, particularly that they're able to isolate it to a
particular cylinder. Any thoughts would be appreciated.

TIA,
George

Through the OBD II interface under the dash. It shows a LOT of info
about the drivetrain. Your brother will probably end up doing a tune up
on the truck (plugs, cap, rotor, wires) then run a can of injector
cleaner through it. Then scan it and see if the code is still there.
AutoZone will scan it for free usually. Good practice to do tune ups at
about 50 K anyway since the plugs will rust into the head if left much
longer, regardless of the hype of 100K tune-ups.

--
Steve W

"ge" > wrote in message
...
> My brother's Safari failed the NYS inspection due to engine codes -
> specifically, "#6 cylinder misfiring." I'm curious as to how they
> detect this, particularly that they're able to isolate it to a
> particular cylinder. Any thoughts would be appreciated.
>
> TIA,
> George



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"Steve W." > wrote in message
...
> Through the OBD II interface under the dash. It shows a LOT of info
> about the drivetrain. Your brother will probably end up doing a tune up
> on the truck (plugs, cap, rotor, wires) then run a can of injector
> cleaner through it. Then scan it and see if the code is still there.
> AutoZone will scan it for free usually. Good practice to do tune ups at
> about 50 K anyway since the plugs will rust into the head if left much
> longer, regardless of the hype of 100K tune-ups.
>
> --
> Steve W
>
> "ge" > wrote in message
> ...
> > My brother's Safari failed the NYS inspection due to engine codes -
> > specifically, "#6 cylinder misfiring." I'm curious as to how they
> > detect this, particularly that they're able to isolate it to a
> > particular cylinder. Any thoughts would be appreciated.
> >
> > TIA,
> > George

Read up on this the other day. Since the computer knows the cylinder which
has just been told to fire, and it has inputs from the crankshaft position
sensor, if the position sensor output shows a lack of acceleration after
ignition of the cylinder, the computer knows that cylinder didn't fire. Bad
runon sentence, but that's the idea. Pretty clever diagnostic, I thought.

Garrett Fulton



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"Steve W." wrote:
>
> Through the OBD II interface under the dash. It shows a LOT of info
> about the drivetrain. Your brother will probably end up doing a tune up
> on the truck (plugs, cap, rotor, wires) then run a can of injector
> cleaner through it. Then scan it and see if the code is still there.
> AutoZone will scan it for free usually. Good practice to do tune ups at
> about 50 K anyway since the plugs will rust into the head if left much
> longer, regardless of the hype of 100K tune-ups.


I think the OP wanted to know how the engine controller detects a
misfire problem and isolates it to a particular cylinder.

I'm not sure, but I'd guess it could be done by monitoring the spark
current for each cylinder and/or data from the knock sensor (similar to
a microphone, its output can be synchronized to the crank position and
firing time).

> --
> Steve W
>
> "ge" > wrote in message
> ...
> > My brother's Safari failed the NYS inspection due to engine codes -
> > specifically, "#6 cylinder misfiring." I'm curious as to how they
> > detect this, particularly that they're able to isolate it to a
> > particular cylinder. Any thoughts would be appreciated.
> >
> > TIA,
> > George
>
> ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
> http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
> ----= East and West-Coast Server Farms - Total Privacy via Encryption =----

--
Paul Hovnanian
------------------------------------------------------------------
Q: Why do mountain climbers rope themselves together?
A: To prevent the sensible ones from going home.

ge wrote:
>
> My brother's Safari failed the NYS inspection due to engine codes -
> specifically, "#6 cylinder misfiring." I'm curious as to how they
> detect this, particularly that they're able to isolate it to a
> particular cylinder. Any thoughts would be appreciated.
>
> TIA,
> George

Just what another poster (gfulton) said, the computer can detect
a billionth of a rpm slowdown due to that cylinder not firing.