Vehicles using Z24S engine list:

Engine Z24S

Symptoms:
- Rough idling and hesitation during acceleration
- Decreased fuel efficiency
- Engine overheating
- Excessive exhaust smoke (blue or black)
- Difficulty starting or stalling

Diagnosis:
- Check for vacuum leaks causing rough idle and poor performance
- Inspect ignition components (spark plugs, wires, distributor cap) for wear or damage
- Test the fuel injection system for clogged injectors or faulty sensors
- Monitor coolant levels and thermostat operation to diagnose overheating
- Examine valve seals and piston rings if blue smoke is present, indicating oil burning

Fixes:
- Replace cracked or disconnected vacuum hoses to restore proper air-fuel mixture
- Change spark plugs and ignition parts as needed to ensure strong spark
- Clean or replace fuel injectors and verify sensor functionality for optimal fuel delivery
- Flush cooling system, replace thermostat, and repair any leaks to prevent overheating
- Perform valve seal replacement or piston ring repair if oil consumption and smoke persist
- Regular oil changes with recommended grade to maintain engine health

Prevention:
- Follow scheduled maintenance including timely oil and filter changes
- Use quality fuel and avoid prolonged idling to reduce carbon buildup
- Regularly inspect and replace worn ignition and fuel system components
- Maintain cooling system by checking coolant levels and condition periodically
- Address minor leaks and engine issues promptly to avoid major repairs

The Z24S engine in Nissan Pathfinder/Terrano models from 1990–1995 is generally reliable but benefits greatly from consistent maintenance and early attention to symptoms to ensure longevity and performance.