Idle screw on NG engine

[DGraber460 at aol.com]

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I saw that post as well. I disagree.
Air _must_ pass into the engine at idle. If the throttle plate is adjusted
properly, it should be nearly closed allowing the idle "bypass" screw to
"fine tune" the amount of air for idle. The ECU can control the amount of
fuel and timing advance, not air. On the CGT it doesn't even get a crack at
the distributor.
I have always adjusted throttle plates with cigarette paper (or onion skin
paper of some sort) to barely get the screw to act as a stop for the plate
coming closed. Then (and only then) turn the idle bypass screw out ~ 1-1/2
turns. This provides a good base level from which to _start_ setting mixture.
Using the throttle plate for adjustment with the bypass seated will work
crudley to accomplish the same end, but doesn't offer anywhere near the
precision of the bypass screw.
Any vacuum leaks take on the role of "air supply", and make these two
components substantially less effective. An idle bypass that has little
effect is a stong indicator that air is coming in elsewhere.
All the components must be balanced in respect to each other. If one changes,
it has a ripple effect through the system, causing all others to try to
compensate.
I'm sure there are going to be some list rebutals, but I have found this to
be functionally effective.

Dennis Graber
Denver
"Good judgement comes from experience, and a lot of that comes from bad
judgement."