1. Check Engine Light:
- If the check engine light is illuminated, it indicates a problem with the engine or emissions system. However, without a scan tool, you won't be able to retrieve detailed fault codes.
2. Fuel Pressure:
- Low fuel pressure can cause the engine to run poorly or even stall. Check the fuel pressure using a pressure gauge to ensure it's within the specified range.
3. Spark Plugs:
- Check the spark plug wires and plugs. Ensure the wires are properly connected and the plugs are not worn or damaged.
4. Fuel Filter:
- A clogged fuel filter can restrict fuel flow to the engine. Check and replace the fuel filter if necessary.
5. Air Filter:
- A dirty air filter can restrict airflow to the engine, causing rough running or poor performance. Check the air filter and replace it if it's clogged.
6. Throttle Body:
- Check the throttle body for carbon buildup or dirt. Clean the throttle body as necessary.
7. Idle Air Control Valve:
- A faulty idle air control valve (IACV) can cause the engine to idle erratically or stall. Try cleaning the IACV to see if it improves the situation.
8. Electrical Connections:
- Check all the electrical connections around the engine, such as battery terminals, fuses, and relays. Ensure they are clean and properly seated.
9. Visual Inspection:
- Perform a thorough visual inspection of the engine compartment. Look for any signs of leaks, damaged components, or loose hoses.
10. Compression Test:
- While it's more challenging without special tools, you can perform a rudimentary compression test by removing the spark plugs and putting your thumb or finger over the spark plug hole while someone cranks the engine. If there's pressure pushing back, there is at least some compression.
11. Fuel Injectors:
- A faulty fuel injector can cause rough idling or misfiring. You can try swapping injectors to see if the problem follows the injector or stays with the cylinder.
12. Vacuum Leaks:
- Listen for any hissing sounds that may indicate a vacuum leak. Spray some carb cleaner around the vacuum hoses and connections while the engine is running. If the engine RPM changes, you may have found the leak.
13. Exhaust System:
- Check for any blockages or leaks in the exhaust system. A clogged catalytic converter can restrict exhaust flow and cause engine problems.
Remember that without a scan tool, your diagnostic capabilities will be limited. If the problem persists or you suspect a more complex issue, it's best to take the vehicle to a qualified mechanic or repair shop for further diagnosis and repairs.
