Dodge ram truck 3500 1996 Service Manual page 1290

14 - 56 FUEL SYSTE.,. - — —
D I A G N O S I S A N D T E S T I N G (Continued)
less than 4.8 volts. The output voltage should
increase gradually as the throttle plate is slowly
opened from idle to WOT.
THROTTLE BODY MINIMUM AIR FLOW CHECK
PROCEDURE—3.9L/5.2L/5.9L ENGINES
The following test procedure has been developed to
check throttle body calibrations for correct idle condi­
tions. The procedure should be used to diagnose the
throttle body for conditions that may cause idle prob­
lems. This procedure should be used only after
normal diagnostic procedures have failed to
produce results that indicate a t h r o t t l e body
related problem. Be sure to check for proper
operation of the idle air control motor before
performing this test.
A special fixed orifice tool (number 6714) (Fig. 73)
must be used for the following test.
SPECIAL TOOL 6714
ll
L
H
)
H
• — *C
J9414-7
Fig. 73 Fixed Orifice Tool
(1) Start the engine and bring to operating tem­
perature. Be sure all accessories are off before per­
forming this test.
(2) Shut off the engine and remove the air cleaner
element housing.
(3) Disconnect the vacuum line at the PCV valve
(Fig. 74).
Fig. 74 install Orifice Tool
B R
(4) Install the 0.185 inch orifice tool (number 6714)
into the disconnected vacuum line in place of the
PCV valve (Fig. 74).
(5) Disconnect the idle purge vacuum line from fit­
ting at throttle body. This vacuum line is located on
the front of throttle body next to the MAP sensor
(Fig. 75). Cap the fitting at throttle body after vac­
uum line has been removed.
^ FRONT O F E N G I N E
THROTTLE
BODY J9414-6
Fig. 75 Idle Purge Line
(6) Connect the DRB scan tool to the 16-way data
link connector. This connector is located under the
instrument panel to the left of the steering column.
Refer to the appropriate Powertrain Diagnostic Pro­
cedures service manual for DRB operation.
(7) Start the engine.
(8) Using the DRB scan tool, scroll through the
menus as follows: select—System, select—Engine,
select—Fuel and Ignition, select—Actuator Tests,
select—Engine rpm and select—Minimum Air Flow.
(9) The DRB scan tool will count down to stabilize
the idle rpm and display the minimum air flow idle
rpm. The idle rpm should be between 500 and 900
rpm. I f the idle speed is outside of these specifica­
tions, replace the throttle body. Refer to Throttle
Body in the Component Removal/Installation section
of this group.
(10) Disconnect the DRB scan tool from the vehi­
cle.
(11) Remove cap from idle purge fitting at throttle
body and install vacuum line.
(12) Remove orifice tool and connect vacuum line
to PCV valve.
(13) Install air cleaner element housing.