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From: MrScottly#54 on 14 Nov 2009 08:50
On Nov 13, 7:33 pm, nobody #1 <rnddma...(a)comcast.net> wrote:
>
>   I do a bit of work on cars emission related systems and momentary
> faults is something I've never heard of. Seen plenty of intermittent
> problems but those are repairable and go away once fixed. What's this
> momentary stuff?


If you get a chance, go look up the lawsuit filed against Toyota by
the Feds about 8 years ago. Here is what was happening with that...

In an OBD2 system, no matter how perfect you make it, there will be
times when, due to environmental factors, that the A/F ratio is not
perfect and thus the tailpipe emmissions are not perfect. This can be
caused by any number of things (plastic bag blows over the snorkle
tube, carbon momentarily sticking in valves, wet plug wire, etc.).
The system does not automatically set a fault if it operates out of
perameters for, let's say, a fraction of a second, then returns to
normal. The system views this as an anomoly and over-looks it. The
system will allow a certain number of these anomolies to occur in a
certain period of time. Too many too soon, it sets a "fault" code.
So, my nomenclature of calling it a "momentary fault" could confuse
and I am sorry I worded it that way. But, back to the system...

Toyota was having a problem meeting the normally accepted "anomoly"
parameters before setting a fault. By government standards, the system
is required to illuminate the Check Engine Light after the same fault
has been found in two different driving cycles, which helps to avoid
CEL illumination for random faults or abnormal conditions. The CEL is
only allowed to extinguish when the same fault has not been detected
on three successive driving cycles.

Toyota got caught reprogramming the ECM's so that they allowed a
greater number of drive cycles before the light came on. Big no-no.

As to what we have now, Harley has benefitted from Delphi technology,
especially the knock sensor technology. That is neat. But, all of it
only goes so far when you have air-cooled cylinders operating at
unstable and inconsistent temps.

Water-cooling is a commin'....


MrScottly#54
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