Engine - Hard Cold Start at High Altitude

Classification:
EC98-026a

Reference:
ITB98-047a

September 15, 1999

1997-99 QX4 HARD START AT HIGH ALTITUDE AND COLD CONDITIONS

This amended version of ITB98-047 updates information in the Applied Vehicles, Applied VINs, Applied Dates and Parts Information sections. Please refer to this bulletin (ITB-047a) for complete information.

Note:
This bulletin supersedes ITB97-025.

APPLIED VEHICLE:
1997-99 QX4 (JR50)

APPLIED VIN:
Vehicles built before JNRAR05Y*XW047868

APPLIED DATE:
Vehicles built before September 4, 1998

SERVICE INFORMATION

If a 1997-99 QX4 is difficult to start at high elevation (over 5,000 ft.) and/or low ambient temperatures after a 4-6 hour cold soak, use this bulletin to diagnose and repair the incident.

The cause may be insufficient air volume through the AAC valve while cranking. New parts (AAC valve assembly and ECM) are available for this incident.

The vehicle may be towed in with a complaint of no start or driven in with a complaint, but no symptoms evident at the time. The incident may be duplicated at the dealership if temperature and altitude match the above referenced conditions.

Hard starting may also occur if base idle speed or ignition timing is out of specification.

SERVICE PROCEDURE

Check for Other Hard-Start Causes

1. A factor which may affect starting performance is the vehicle oil viscosity. API SG or SH rated 5W-30 motor oil is preferred for most Nissan models. In colder weather, 5W-30 rated oil will make starting easier and maintain a more stable idle during warm-up. This is due to the lower viscosity of 5W-30 at lower temperatures compared to 10W-30.

2. Before installing new parts, make sure of the following:

^ Check the engine oil level. If the engine oil level is low, add oil as needed. If the engine oil level is high (above the "H" mark on the dipstick) and the oil has a gasoline odor, change the engine oil and filter before proceeding.

^ Battery fully charged; battery cables and terminals clean and tight.

^ Fuel pump function is OK (squeeze the fuel line with your fingers and feel for pressure when the key is turned to the "on" position).

^ Compression is OK.

^ Use CONSULT to check for any related diagnostic trouble codes (e.g.: injectors, ignition system, etc.) and repair as needed.

Start Engine - Check Base Idle Speed and Ignition Timing

1. Try to start the engine. Fully depress the accelerator during cranking.





2. If the engine does not start, temporarily remove the fuel pump fuse (see Figure 1) or turn the pump fuse off with CONSULT work support. With the accelerator pedal fully depressed, crank the engine for 5 - 10 seconds to clear excess fuel from the combustion chambers.

3. Once the engine has started, warm it up until the engine coolant temperature indicator points to the middle of the gauge. After the normal operating temperature is reached, ensure engine speed remains below 1,000 rpm.

4. At normal operating temperature, run the engine at about 2,000 rpm for approximately 2 minutes under no-load. Race the engine (2,000 - 3,000 rpm) 2 or 3 times under no-load, then run the engine at idle speed for 1 minute.





5. Turn off the engine and disconnect the throttle position sensor harness connector (see Figure 2). Re-start the engine and rev (2,000 - 3,000 rpm) 2 or 3 times under no-load, then run the engine at idle speed.





6. Check the engine timing with a timing light (see Figure 3). (Specification is: 15° +/- BTDC in "N" position)

a. If the timing is correct, proceed to step 7.

b. If necessary, adjust the ignition timing to the specified value by rotating the distributor after loosening the securing bolts. Then turn off engine and connect the throttle position sensor harness connector to the throttle position sensor and repeat steps 3 - 6.

7. At normal operating temperature, rev the engine (2,000 - 3,000 rpm) 2 or 3 times under no-load, then run the engine at idle speed.

8. Check the base idle speed (Specification is: 700 +/- 50 rpm in "N" position).

a. If the base idle speed is correct, proceed to step 9.





b. If necessary, adjust the base idle speed by turning idle speed adjusting screw (see Figure 4). and repeat steps 7 - 8.

9. Turn the engine off and reconnect the throttle position sensor harness connector.

10. Start engine and rev (2,000 3,000 rpm) 2 or 3 times under no-load, then run the engine at idle speed.

11. Use CONSULT to clear any TPS DTC and verify that no new DTC has been set during the above procedure.

NOTE:
If either the ignition timing or the base idle speed required adjustment, correcting this condition should resolve the "crank, but no start" incident.

Replace the ECM and the AAC Valve

If both the ignition timing and base idle speed have been inspected with the service procedure in this bulletin and required no adjustment, do the following:

1. Replace the ECM and the AAC valve with the new parts listed in the Parts Information table.

NOTE:
The ECM and AAC Valve MUST be installed as a set. The new ECM is labeled: "Installed per ITB98-047". It is accompanied with a label to be secured to the new AAC valve.

2. After installation of the ECM, locate the label found in the ECM box.





3. Before installation of the AAC valve, secure the label found in the ECM box to the AAC valve as shown in Figure 5.

4. Install the new AAC valve.

5. Recheck the base idle as outlined in steps 1 through 11.

NOTE:
It is not necessary to recheck the ignition timing in step 6.

6. Use CONSULT to clear any DTCs. Road test the vehicle to ensure no other driveability issues are present.





PARTS INFORMATION

IMPORTANT:
If either the AAC valve or the ECM need replacement in the future, you must use the parts information from this bulletin.





CLAIMS INFORMATION