Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSNISSAN-DATSUN2004SENTRA L4-2.5L (QR25DE)REPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTIGNITION SYSTEMIGNITION TIMINGADJUSTMENTS
2004 Nissan-Datsun Sentra L4-2.5L (QR25DE)
Ignition Timing: Adjustments
2004 Nissan-Datsun Sentra L4-2.5L (QR25DE)SECTION Adjustments
Idle Speed/Ignition Timing/Idle Mixture Ratio Adjustment (A/T MODELS ULEV AND M/T MODELS)
PREPARATION
1. Make sure that the following parts are in good order.
- Battery
- Ignition system
- Engine oil and coolant levels
- Fuses
- ECM harness connector
- Vacuum hoses
- Air intake system
(Oil filler cap, oil level gauge, etc.)
- Fuel pressure
- Engine compression
- Throttle valve
- Evaporative emission system
2. On air conditioner equipped models, checks should be carried out while the air conditioner is OFF.
3. On automatic transmission equipped models, when checking idle rpm, ignition timing and mixture ratio, checks should be carried out while shift lever is in N position.
4. When measuring CO percentage, insert probe more than 40 cm (15.7 in) into tail pipe.
5. Turn off headlamps, heater blower, rear window defogger.
6. Keep front wheels pointed straight ahead.
OVERALL INSPECTION SEQUENCE
INSPECTION PROCEDURE
Idle Speed/Ignition Timing/Idle Mixture Ratio Adjustment (A/T MODELS EXCEPT ULEV)
PREPARATION
1. Make sure that the following parts are in good order.
- Battery
- Ignition system
- Engine oil and coolant levels
- Fuses
- ECM harness connector
- Vacuum hoses
- Air intake system
(Oil filler cap, oil level gauge, etc.)
- Fuel pressure
- Engine compression
- Throttle valve
- Evaporative emission system
2. On air conditioner equipped models, checks should be carried out while the air conditioner is OFF.
3. On automatic transmission equipped models, when checking idle rpm, ignition timing and mixture ratio, checks should be carried out while shift lever is in N position.
4. When measuring CO percentage, insert probe more than 40 cm (15.7 in) into tail pipe.
5. Turn off headlamp, heater blower, rear window defogger.
6. Keep front wheels pointed straight ahead.
7. Perform inspection after the cooling fans have completely stopped.
OVERALL INSPECTION SEQUENCE
INSPECTION PROCEDURE
PREPARATION
1. Make sure that the following parts are in good order.
- Battery
- Ignition system
- Engine oil and coolant levels
- Fuses
- ECM harness connector
- Vacuum hoses
- Air intake system
(Oil filler cap, oil level gauge, etc.)
- Fuel pressure
- Engine compression
- Throttle valve
- Evaporative emission system
2. On air conditioner equipped models, checks should be carried out while the air conditioner is OFF.
3. On automatic transmission equipped models, when checking idle rpm, ignition timing and mixture ratio, checks should be carried out while shift lever is in N position.
4. When measuring CO percentage, insert probe more than 40 cm (15.7 in) into tail pipe.
5. Turn off headlamps, heater blower, rear window defogger.
6. Keep front wheels pointed straight ahead.
Overall Inspection Sequence:
OVERALL INSPECTION SEQUENCE
Inspection Procedure (Steps 1 - 2):
Inspection Procedure (Steps 3 - 5):
Inspection Procedure (Steps 6 - 9):
Inspection Procedure (Steps 10 - 14):
Inspection Procedure (Steps 15 - 18):
Inspection Procedure (Steps 19 - 22):
Inspection Procedure (Steps 23 - 26):
Inspection Procedure (Steps 27 - 31):
Inspection Procedure (Steps 32 - 33):
INSPECTION PROCEDURE
Idle Speed/Ignition Timing/Idle Mixture Ratio Adjustment (A/T MODELS EXCEPT ULEV)
PREPARATION
1. Make sure that the following parts are in good order.
- Battery
- Ignition system
- Engine oil and coolant levels
- Fuses
- ECM harness connector
- Vacuum hoses
- Air intake system
(Oil filler cap, oil level gauge, etc.)
- Fuel pressure
- Engine compression
- Throttle valve
- Evaporative emission system
2. On air conditioner equipped models, checks should be carried out while the air conditioner is OFF.
3. On automatic transmission equipped models, when checking idle rpm, ignition timing and mixture ratio, checks should be carried out while shift lever is in N position.
4. When measuring CO percentage, insert probe more than 40 cm (15.7 in) into tail pipe.
5. Turn off headlamp, heater blower, rear window defogger.
6. Keep front wheels pointed straight ahead.
7. Perform inspection after the cooling fans have completely stopped.
Overall Inspection Sequence:
OVERALL INSPECTION SEQUENCE
Inspection Procedure (Steps 1 - 2):
Inspection Procedure (Steps 3 - 5):
Inspection Procedure (Steps 6 - 10):
Inspection Procedure (Steps 11 - 16):
Inspection Procedure (Steps 17 - 19):
Inspection Procedure (Steps 20 - 22):
Inspection Procedure (Steps 23 - 26):
Inspection Procedure (Steps 27 - 30):
Inspection Procedure (Steps 31 - 33):
INSPECTION PROCEDURE
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.