Vehicles using 12ST engine list:

Engine 12ST

Symptoms:
- Rough idling and stalling, especially when cold
- Loss of power or poor acceleration
- Increased fuel consumption
- Engine misfires or hesitation during throttle response
- Occasional difficulty starting the engine

Diagnosis:
- Check for vacuum leaks around intake manifold and hoses, as these are common in older 12ST engines
- Inspect ignition system components: spark plugs, distributor cap, rotor, and ignition wires for wear or corrosion
- Test fuel delivery system including fuel filter and carburetor or fuel injection components for clogging or malfunction
- Examine timing belt or chain condition and timing settings, as incorrect timing affects performance
- Look for signs of worn valve seals or piston rings causing compression loss

Fixes:
- Replace cracked or brittle vacuum hoses and gaskets to eliminate leaks
- Renew spark plugs and ignition components as needed to restore proper firing
- Clean or rebuild carburetor; replace fuel filter to ensure adequate fuel flow
- Adjust or replace timing belt/chain to correct engine timing
- Perform a compression test; if low, consider valve seal replacement or piston ring repair
- Regular oil changes with recommended grade to maintain engine lubrication and reduce wear

Prevention:
- Follow scheduled maintenance intervals for ignition system and fuel filters
- Regularly inspect and replace aging vacuum lines and gaskets to prevent leaks
- Use quality fuel and oil to minimize deposits and wear
- Monitor engine performance and address symptoms early to avoid major repairs
- Keep timing components serviced to maintain engine efficiency and longevity