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5B.23
Section 5B
EFI Fuel System
5B
gradually increase to the established setting as
operation continues. Do not attempt to circumvent this
warm up period, or readjust the idle speed during this
time. The engine must be completely warmed up for
accurate idle speed adjustment.
Adjustment Procedure
1. Make sure there are no fault codes present in the
ECU memory.
2. Start the engine and allow it to fully warm up and
establish closed looped operation (approximately
5-10 min.).
3. Place the throttle control in the ‘‘idle/slow’’ position
and check the idle speed with a tachometer. Turn
the idle speed screw in or out as required to obtain
1500 RPM, or the idle speed specified by the
equipment manufacturer.
4. The low idle speed adjustment can affect the high
speed setting. Move the throttle control to the full
throttle position and check the high speed. Adjust
as necessary to 3750 RPM (no load), or the speed
specified by the equipment manufacturer.
Idle Speed Screw Dampening Spring
A small dampening spring (Kohler Part No.
24 089 42-S) is attached to the end of the idle speed
screw of some EFI engines to help stabilize no load
operating speeds. See Figure 5B-36.
Figure 5B-36. Idle Speed Screw Details.
Figure 5B-35. Upper Intake Manifold.
General
The EFI engines have no carburetor, so the throttle
function (regulate incoming combustion airflow) is
incorporated in the intake manifold assembly. The
manifold consists of a one-piece aluminum casting
which also provides mounting for the fuel injectors,
throttle position sensor, fuel rail, air baffle, idle speed
screw, and air cleaner assembly.
Service
The throttle body/intake manifold is serviced as an
assembly, with the throttle shaft, throttle plates, and
idle speed adjusting screw installed. The throttle shaft
rotates on needle bearings (non-serviceable), capped
with rubber seals to prevent air leaks.
Idle Speed Adjustment (RPM)
General
The idle speed is the only adjustment that may be
performed on the EFI system. The standard idle speed
setting for EFI engines is 1500 RPM, but certain
applications might require a different setting. Check
the equipment manufacturer’s recommendation.
For starting and warm up, the ECU will adjust the fuel
and ignition timing, based upon ambient temperature,
engine temperature, and loads present. In cold
conditions, the idle speed will probably be higher than
normal for a few moments. Under other conditions, the
idle speed may actually start lower than normal, but
1-3 mm (0.039-0.117 in.)
Exposed Length Off End
Of Adjustment Screw
Idle Speed Screw
Dampening
Spring
(some models)
Fuel Rail
Throttle Body
Intake Manifold
Low Idle Speed
Adjusting Screw
CAUTION: Standard fuel line is not
compatible and must not be used! Use only Oetiker
clamps (Kohler Part No. 24 237 05-S) on fuel line
connections.
Throttle Body/Intake Manifold Assembly