Ronald Wong wrote:
> I guess I don't understand. I think I need a scan tool to check this out.
Sorry for the confusion - let me see if I can help sort this out. My previous
post about the onset of closed loop was referring to just the cold start
condition.
> I thought the way we drove that we would be in open loop most of the
> time...since closed loop occurs only during cruising down the road at set
> speeds.
The only time you are in open loop is at cold start or when the computer sees an
abrupt change in either map or tps (like a WOT stab). This also means that 99.9
percent of the time you are in closed loop unless you drive around with the
accelerator glued to the floorboard.
> During engine warm-up the PCM is supposed to ignore O2 sensors and
> stay in open loop.
This is correct to an extent. To rephrase more accurately: "During O2 sensor
warm-up, the PCM will ignore O2 sensors and be in open loop". It only takes a
short while (seconds/minutes) for them to get hot enough (around 600 degrees F)
for the PCM to transition into closed-loop where it stays MOST of the time.
> Open loop is also supposed to occur when TPS senses an
> abrupt increase or MAP sensor indicates an abrupt increase.
This is also correct. Just realize that it takes almost a WOT stab to make it
transition to open loop. Read "not very often".
Hope this helps - 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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