Engine Controls - Adjustments - 8.0l Dodge Pickup R3500

ENGINE MECHANICAL

Before performing any on-vehicle adjustments to fuel or ignition systems, ensure engine mechanical condition is okay.

VALVE CLEARANCE

Note. All engines use hydraulic lifters. No adjustments are required.

IGNITION TIMING

Ignition timing is controlled by Powertrain Control Module (PCM). Ignition timing is nonadjustable. DO NOT attempt to adjust ignition timing by rotating distributor.

Note. If distributor is rotated, fuel system synchronization will be changed. If distributor is removed or rotated, check fuel system synchronization. See FUEL SYSTEM SYNCHRONIZATION under FUEL SYSTEM.

FUEL SYSTEM SYNCHRONIZATION

Note. Fuel system synchronization is controlled by position of the distributor. Rotating distributor WILL NOT change ignition timing, but will change fuel system synchronization. Fuel system synchronization should be checked anytime distributor is removed or rotated.

1. Connect scan tool to Data Link Connector (DLC). DLC is located below driver's side of instrument panel, near steering column. (Scheme 1)
2. Using scan tool manufacturer's instructions, access SET SYNC display on scan tool. Following scan tool displays, start engine. Warm engine to normal operating temperature. With engine idling, if scan tool displays IN RANGE along with 0°, this indicates correct distributor location. The degree reading displayed on scan tool indicates the fuel synchronization, not ignition timing.
3. If scan tool display is correct, shut engine off. Remove scan tool. If scan tool does not display IN RANGE along with 0°, go to next step.
4. If scan tool displays a plus (+) or minus (-) sign next to the degree number, and/or the degree number displayed is not zero, loosen but DO NOT remove distributor hold-down bolt.
5. Rotate distributor until scan tool displays IN RANGE. Continue to rotate distributor until a reading as close as possible to 0° is obtained. Tighten distributor hold-down bolt to 16 ft. lbs. (22 N.m). Shut engine off. Remove scan tool.

Scheme 1

IDLE SPEED & MIXTURE

Idle speed and mixture are controlled by Powertrain Control Module (PCM). No adjustment is required. PCM controls Idle Air Control (IAC) motor for proper idle speed. See appropriate TESTS W/CODES article for diagnosis of incorrect idle speed or IAC motor operation.

THROTTLE BODY MINIMUM AIRFLOW

Note. Throttle body minimum airflow procedure checks throttle body calibration for correct idle speed. Procedure may be used for idle speed problems caused by the throttle body. Throttle body minimum airflow procedure should be performed after all other diagnostic procedures have failed to produce results that indicate a throttle body related problem. Ensure IAC motor is operating correctly before performing this procedure.

Throttle body minimum airflow cannot be checked on this application.

THROTTLE POSITION SENSOR

Note. Throttle Position (TP) sensor is nonadjustable. Use following procedure to check TP sensor calibration. For complete testing of TP sensor and wiring circuit, see appropriate TESTS W/CODES article.

1. Remove components for access to electrical connector at TP sensor mounted on throttle body. With electrical connector installed on TP sensor, turn ignition on with engine off. DO NOT start engine.
2. Using digital volt-ohmmeter, measure voltage at center terminal on electrical connector for TP sensor with throttle valve closed (idle position). Voltage should be greater than .35 volt, but less than .90 volt.
3. Slowly open throttle to full throttle and note voltage reading. Voltage should smoothly increase to less than 4.50 volts. Replace TP sensor if voltage is not within specification.