Throttle Body Setup Adjustment
Republished from http://www.paladinmicro.com
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Aftermarket throttle bodies allegedly have the throttle valve
(butterfly) properly set when they leave the factory, however I
have seen a number of posts on the forums from people who had idle
problems after installing an aftermarket TB and either did not know
what to do, or decided to muck about with the throttle valve stop
screw (aka "idle screw", which it really isn't).
The PCM can tolerate and correct for a lot of things that are
not entirely perfect, however a lot of what it does is based upon
an assumption of certain base settings. The base throttle body idle
stop screw setting is one of those things. Some have been lucky and
solved their problems, other have gotten things so messed up that
they sent the new TB back and reinstalled the stock unit.
Here is the procedure for resetting the throttle valve back to
it's proper initial position.
- Loosen the adjustment screw locknut, and turn the throttle stop
screw anti-clockwise (loosen it) until you can see the gap between
it and the throttle linkage lever;
- Using a feeler gauge adjust the screw until there is 0.010"
clearance between the screw and the throttle lever;
- Turn the screw clockwise (tighten it) one full turn;
- Start the engine to check idle speed, if too high turn the crew
anti-clockwise in small increments (1/16 turn) until the idle speed
is as you like; if too low then turn the screw clockwise in small
increments;
- Hold the stop-screw screw in position and tighten the
locknut;
If there is any binding of the throttle plate at tip-in then
loosen the locknut and turn the adjusting screw clockwise very
slightly (no more than 1/8th turn) to eliminate the
binding--retighten the lock nut of course.
It's not a bad idea at this point to disconnect the battery for
5-7 minutes to clear the PCM's KAM (Keep Alive Memory). This is
where all learned parameters, such as idle air and fuel trim values
are stored. Clearing the KAM will force the PCM to relearn these
values.
If the idle is still not as you would like (it should be, but
there's a slim possibility it may not be) repeat step 4.
Here's a photo of the throttle stop screw: