TommFern@aol.com wrote:
> Sure, I understand that. Let me try and rephrase the question. Lets say that
> the O2 sensor sees a extreme lean condition at idle. It tries to compensates
> by increasing the pulse width as far as its parameters will let it. When this
> occurs, is the maximum pulse width the PCM will allow, period?
Thats almost exactly the way I understand it to be also Tom. I've heard that at
this point a MIL is flagged. The code is something like Injector X failed to
respond to control circuit supposedly. The key component is the O2 sensor
feedback - if the Max Inj Ontime has been reached and the O2 doesn't respond w/a
rich condition - the MIL is set. I'm not sure why it picks a particular injector
- may be the particular one that it is gnding at the time. On the flip side -
lets say you install 24lb injectors and are sitting there idling and the O2
sensor is reading rich. The pcm cuts the inj ontime until it is at the min - if
the O2 sensor still reads rich - the SAME type of MIL is set (inj y failed to
respond to control circuit).
I would have to mention the O2 voltage too high and O2 sensor voltage too low
codes also because someone is gonna ask about those. These relate to O2 sensor
"cross-counts" or lack thereof from what I understand. By cross-counts, I mean
voltage crossing the "magic" 0.45V mark (14.7 to 1). The O2 sensor gets a bias
voltage of exactly that magic voltage and if it never changes - it must not be
working. Unplugging it will verify that for sure. Supposedly the PCM (and O2)
are so sensitive that O2 sensor tests are regularly performed (mandated by OBD2
regs) for a certain number of cross-counts per unit time to verify the O2 sensors
performance. Once degraded - a MIL is set.
Some automotive type multimeters can directly measure inj ontime (or is it duty
cycle?) so maybe someone with one of these will bring it to the next DML meet and
we could test this assuming we could find a truck that could predict an "inj
failed to respond" MIL.
Whaddya think?
Latr,
Shane
-- '96 IndyRam-HisIndy-MPI/TB/Pulleys/AccelCoil/MPComp/HookerSuperComps/CompTAs '96 IndyRam-HerIndy-numbered(#142)"Track Truck" '74 Triple-Black Dodge Challenger Rallye 360 home-brew EFI R&D vehicle '68 Black Corvette Convertible 427 (For Sale)
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