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Re: Stuttering

Jim Adney wrote:

>>Why the voltage regulator would cause a rich running solution is a mystery to
>>me, though. 
>The system voltage also supplies the FI brain. I don't know exactly why it 
>makes it richer, but it does.
My guess is this:

The head temp sensor sends to the brain a voltage value based on the
resistance of the sensor. At a specific given temp, the sensor's
resistance is constant (at 60 deg, the resistance is x, and 90, the
resistance is y) so if the sensor is operating on a 14v system, the
voltage signal being sent by the sensor to the brain is known and
predictable. Now, what happens if you lower the voltage significantly?
The voltage coming out of the sensor has shifted downward, also, sending
a signal to the brain that the sensor is operating at a voltage for a
different expected temp. We know the head sensor is the main input on
whether cold  enrichment is necessary. I believe the resistance of the
head temp sensor is highest the colder it is. If it's getting less
voltage as input, it will proportionately supply less voltage signal to
the brain, tricking the brain into thinking it's colder. If the brain
THINKS its colder than it is, then that would explain how lower than
expected voltage would make a car run richer than necessary. By this
argument, too high a voltage would make a car run leaner, but in my
experience with most cars voltage regulators tend to fail on the "too
low voltage" side.

I'd go out on a limb and say 95% of the cause of "low voltage running
rich" is this head sensor thing.

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