ENGINE MECHANICAL
Note. The Assembly Line Data Link (ALDL) connector may also be referred to as the Data Link Connector (DLC). The SERVICE ENGINE SOON (SES) light may also be referred to as the Malfunction Indicator Light (MIL).
Before performing any on-vehicle adjustments to fuel or ignition systems, ensure engine mechanical condition is okay.
VALVE CLEARANCE
Note. All models use hydraulic lifters. No adjustments are required.
IGNITION TIMING (GASOLINE)
Note. Ignition timing is controlled by control module and is not adjustable.
Note. If distributor removal is necessary, see DISTRIBUTOR in the Removal & Installation article before proceding.
CHECKING/ADJUSTING INJECTION TIMING
Original factory injection pump timing is marked with a static timing mark, a line scribed across both the pump mounting flange and the front cover. This static timing mark should be used as a reference. If timing mark is not present on mounting flange, scribe a line to assist in how far injection pump needs to be rotated.
- Start and warm engine to normal operating temperature. Connect Tech 1 scan tester. Set scan tester to OUTPUT TEST/INJ PUMP mode. Activate TDC TIME SET. The DESIRED INJ TIM value will read zero. NOTE: If engine stalls when TDC TIME SET is activated, turn engine off. Loosen injection pump nuts. Slightly rotate injection pump toward driver's side of vehicle. Tighten injection pump nuts. Repeat step 1).
- Ensure engine is running, then check "MEASURED INJ TIM" for proper timing specification. See DIESEL INJECTION PUMP TIMING table. If timing needs adjustment, turn engine off to avoid engine damage, then adjust injection pump. A 1-mm pump movement equals about 2 degrees timing.
| Application | Man. Trans. | Auto. Trans. |
|---|---|---|
| 6.5L (VIN F, P & S) | 3.5 @ Idle | 3.5 @ Idle |
DIESEL INJECTION PUMP TIMING (DEGREES BTDC @ RPM)
TDC OFFSET LEARN PROCEDURE
Note. It takes PCM 20 seconds to learn TDC offset.
This procedure is only used when one of following conditions exists
- Front cover and PCM are removed and replaced at same time.
- Injection pump and PCM are removed and replaced at same time.
- Front cover and/or crank sensor, pump and PCM are removed and replaced at same time.
- Front cover has been removed.
- Engine has been replaced. Start and warm engine to normal operating temperature. Connect Tech 1 scan tool. Using scan tester, select OUTPUT TEST or INJECTION PUMP mode, and activate TDC OFFSET LEARN. NOTE: If engine stalls when "TDC TIME SET" is activated, turn engine off. Loosen injection pump nuts. Slightly rotate injection pump toward driver's side of vehicle. Tighten mounting nuts and repeat step 1). If learned TDC OFFSET reading is between .00 and -.50 degrees, procedure is complete. If reading is not as specified, slightly rotate injection pump and repeat step 1). A 1-mm pump movement equals about 2 degrees timing. To achieve a negative reading, rotate pump toward driver's side. To achieve a positive reading, rotate pump toward passenger's side.
IDLE SPEED & MIXTURE (GASOLINE)
Note. DO NOT attempt to adjust idle mixture and idle speed. Both are controlled by Powertrain Control Module (PCM). Incorrect idle speeds are normally caused by dirty throttle plate or vacuum leaks. Ensure all vacuum components are functioning properly.
Note. Controlled idle speed and IAC count can be checked using scan tester. See CONTROLLED IDLE SPEED & IAC COUNT table. Minimum idle speed adjustment can only be performed on the 7.4L engines. See MINIMUM IDLE SPEED ADJUSTMENT (7.4L).
Controlled Idle Speed Check
- Ensure no trouble code(s) are present, IAC system is okay, and ignition timing is correct. Block drive wheels. Apply parking brake. Connect Tech 1 scan tester to Data Link Connector (DLC). Put scan tester into OPEN mode.
- Start engine and bring to normal operating temperature. Check for correct state of park/neutral switch on scan tester. Check if idle speed and IAC valve pintle position (counts) are as specified. See CONTROLLED IDLE SPEED & IAC COUNT table.
- If idle speed is not within specification, refer to TESTS W/O CODES article. On 7.4L engines, perform MINIMUM IDLE SPEED ADJUSTMENT.
| Application | Idle RPM | (1) IAC Counts | |
|---|---|---|---|
| 4.3L CSI | |||
| Auto. Trans. (2) (3) | 537 | 5-30 | |
| Auto. Trans. (2) (3) | 650 | 5-30 | |
| Man. Trans. (4) | 550 | 5-30 | |
| 5.0L CSI | |||
| Auto. Trans. (2) | 500 | 5-30 | |
| Man. Trans. (4) | 600 | 5-30 | |
| 5.7L CSI Under 8500 GVW | |||
| Auto. Trans. (2) | 550 | 5-30 | |
| Man. Trans. (4) | 700 | 5-30 | |
| 5.7L CSI Over 8500 GVW | |||
| Auto. Trans. (2) | 550 | 5-30 | |
| Man. Trans. (4) | 600 | 5-30 | |
| 7.4L CSI | |||
| Auto. Trans. (2) | 675 | 5-30 | |
| Man. Trans. (4) | 700 | 5-30 | |
| (1) Add 2 counts for engines with less than 500 miles. On 4.3L and V8 engines, add 2 counts for every 1000 ft. above sea level. (2) Automatic transmission in Drive. (3) Calibration identification is not given by manufacturer. IAC count and actual RPM should correspond to one of these calibrations. (4) Manual transmission in Neutral. Tech 1 scan tester will display "RDL" with transmission in Neutral. | |||
| (1) | Add 2 counts for engines with less than 500 miles. On 4.3L and V8 engines, add 2 counts for every 1000 ft. above sea level. |
| (2) | Automatic transmission in Drive. |
| (3) | Calibration identification is not given by manufacturer. IAC count and actual RPM should correspond to one of these calibrations. |
| (4) | Manual transmission in Neutral. Tech 1 scan tester will display "RDL" with transmission in Neutral. |
CONTROLLED IDLE SPEED & IAC COUNT
Minimum Idle Speed Adjustment (7.4L)
- Check controlled idle speed and perform IAC system check first. Refer to CONTROLLED IDLE SPEED CHECK. Set parking brake and block drive wheels. Start engine and operate to normal operating temperature of about 185-212°F (85-100°C). Turn engine off.
- Remove air cleaner, adapter and gaskets. Ensure throttle lever is not binding TV cable or cruise control cable. At Diagnostic Link Connector (DLC), ground the White/Black wire terminal (upper row, second terminal from right end). Turn ignition on (engine off). Wait for at least 10 seconds (this allows IAC pintle to extend and seat in throttle body).
- Disconnect IAC valve harness connector. Remove jumper from DLC. Connect scan tester to DLC. Put scan tester into OPEN mode. Place transmission in Neutral. Start engine. Allow engine RPM to stabilize. Check engine RPM. See MINIMUM IDLE SPEED table. Disregard IAC count on scan tester while IAC valve is disconnected.
- If idle speed is not as specified, remove stop screw plug by using an awl. With engine at normal operating temperature, adjust stop screw to obtain nominal RPM with seated IAC valve. Turn ignition off. Reconnect IAC harness connector. Disconnect scan tester. Reseal stop screw hole and reinstall air cleaner assembly.
- Reset IAC valve as follows: Turn ignition on (engine off) for 5 seconds. Turn ignition off for 10 seconds. Start engine. If engine does not idle correctly, repeat procedure.
| Application | RPM |
|---|---|
| Automatic Transmission (In Drive) | 600-650 |
| Manual Transmission (In Neutral) | 675-725 |
| (1) If engine has less than 500 miles or if checking idle speed at altitudes above 1500 feet, idle speed with seated IAC is lower than specified. | |
| (1) | If engine has less than 500 miles or if checking idle speed at altitudes above 1500 feet, idle speed with seated IAC is lower than specified. |
MINIMUM IDLE SPEED (1) (7.4L)
IDLE SPEED (DIESEL)
Idle speed is not adjustable. PCM controls all fuel delivery/modes based on inputs from AAP, ECT and BARO sensors. System is equipped with an electronic fuel injection pump.
ALL GASOLINE ENGINES
TP sensor output voltage should be .85 volt or less at idle (closed throttle) and is not adjustable.
6.5L DIESEL
Throttle control is electronic with NO mechanical link from engine to accelerator pedal. The PCM monitors the position of accelerator pedal based on signals from a non-adjustable Accelerator Pedal Position (APP) module. The APP is mounted above the accelerator pedal.
See also:
• DISTRIBUTOR