Page: 4-62
WALKER MANUFACTURING COMPANY
July 2006
SERVICE INSTRUCTIONS
Throttle Body/Intake Manifold Assembly - Model
MTEFI
Upper Intake Manifold
General
The EFI engines have no carburetor, so the throttle
function (regulate incoming combustion airflow) is in-
corporated in the intake manifold assembly. The man-
ifold consists of a one-piece aluminum casting which
also provides mounting for the fuel injectors, throttle po-
sition sensor, fuel rail, air baffle, idle speed screw, and
air cleaner assembly.
Service
The throttle body/intake manifold is serviced as an as-
sembly, with the throttle shaft, throttle plates, and idle
speed adjusting screw installed. The throttle shaft ro-
tates on needle bearings (non-serviceable), capped
with rubber seals to prevent air leaks.
Idle Speed Adjustment (RPM) - Model MTEFI
General
The idle speed is the only adjustment that may be per-
formed on the EFI system. The standard idle speed
setting for EFI engines is 1500 RPM, but certain appli-
cations 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 condi-
tions, 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 gradu-
ally 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 - Model
MTEFI
A small dampening spring (Kohler P/N 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.
Refer to Idle Speed Screw Details illustration.
Idle Speed Screw Details
Low Idle Speed
Adjusting Screw
Throttle Body
Intake Manifold
Fuel Rail
1-3 mm (0.039-0.117 in.)
Exposed Length Off End
Of Adjustment Screw
Idle Speed Screw
Dampening
Spring
(Some Models)
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