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Idle speed adj for '81-up 931 (+throttle stop set procedure)

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Location: DE (the one near MD, PA, NJ)

PostPosted: Wed Mar 08, 2006 5:21 am    Post subject: Idle speed adj for '81-up 931 (+throttle stop set procedure) Reply with quote

If the throttle stop was, or may have been messed-with, first perform the "*-Throttle Stop setting procedure -" down below.

Idle speed setting procedure -
You use a timing light to set the idle on an '81-up 931 because of the EIS (electronic idle stabilization) which automatically alters the timing to control the idle speed (and EIS is built in to the DITC box, rather than being seperate and seperately disable-able as on the '81-up 924NA with TCI-H ignition). The procedure involves warming the engine plus some other details, then you adjust the idle setscrew while watching the flywheel with a timing light and adjust the idle screw to get the "o" (or "0") mark lined-up.

1) Get a timing light and an M14x1.5 threaded plug (I made one from an end fitting that was removed from a used fuel filter).
2) Remove the intake air temp sensor and screw in the M14x1.5 plug in its' place to close the hole. Plug the sensor back in with its' connector and place it up in the cooler area near the windshield wiper motor.
3) Start and fully warm the engine.
4) As a mark, you may have a dot "o" (earlier) or an oval "0" (later). If the dot, adjust the idle screw (the large vertically-oriented screw at lower left of pic below) 'til it's fully visible right at the bottom of the flywheel window. If you have the oval, adjust 'til it's half visible at the bottom of the window. "Back and forth motion of mark indicates that ignition system is being regulated." -So you'll probably see the mark appear and disappear - adjust so that when it appears, it's lined-up there at the bottom of the window. (If your timing light is adjustable, set it to zero.)

If and when the air:fuel mix is adjusted, the above procedure should be gone through again to re-set the idle.


*-Throttle Stop setting procedure -
It's set at the factory, does not normally require adjustment, bla bla..
1) back off the adjusting screw until there is clearance between its' tip and the throttle valve lever
2) place a thin piece of paper between the screw tip and throttle lever
3) turn the screw in until it lightly contacts the paper (basically using the paper as a feeler gauge)
4) from this position, remove the paper and turn the screw in an additional 1/2 turn

Showing a series 2 ('81-up) 931 TB, the throttle stop is the small screw just below dead center in this pic (the idle setting is set vertically via the larger screw at lower-left) -

"'s made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox
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