Fuel-injected engines don’t have a distributor, therefore, they don’t have points. Instead, timing is controlled by the Engine Control Unit (ECU) utilizing data gathered from several sensors placed around the engine. It uses this information to calculate when the spark plug should fire and how much fuel should be injected into the cylinders.
Basic Ignition System Checkup
If your modern fuel-injected engine is experiencing rough idle or hesitation when accelerating or if the check engine light is illuminated, your first move is to perform a basic ignition system checkup.
1. Visual inspection: Lift the hood and inspect all of the spark plug wires and connectors for any signs of cracking, arcing, or corrosion. Replace them as needed.
2. Spark plugs: Next, check the spark plugs for wear and deposits. If they’re worn or fouled, replace them with new ones using the specified gap distance.
3. Battery terminals: Also, inspect the battery terminals and clean them if needed to ensure a good electrical connection.
4. Fuel filter: And lastly, check and replace the fuel filter if necessary.
Fuel Pressure Test
A malfunctioning fuel pump won’t supply sufficient pressure for proper operation. To verify that the pump is working properly, you’ll need to perform a fuel pressure test. Fuel injection systems operate at a much higher pressure than carbureted engines, be sure to consult a repair manual for the recommended pressure for your vehicle.
Vacuum Leaks Checkup
Vacuum leaks are another common reason for hesitation or erratic idle in the modern day fuel-injected engines. This happens because air is introduced through the vacuum leak, which upsets the fuel-to-air mixture.
The quickest way to diagnose vacuum leaks is to spray carburetor cleaner or starting fluid while the engine is running. Listen for any changes in the idle quality. If it stumbles, you’ve found your leak. Make necessary repairs to seal or replace any cracked, loose or damaged vacuum lines.
Diagnostic Troubleshooting
If your fuel-injected engine is still experiencing problems, you’ll need a way to gather more information about what’s going on within. For this purpose, you can either connect a scan tool to the vehicle or use an OBD-II (On-Board Diagnostics II) code reader. Both methods will provide you with DTCs, which are diagnostic trouble codes. These are unique 5-digit numbers that specify the engine malfunction detected.
If you encounter a particular DTC, the next step is to follow a diagnostic chart or flowchart as presented in a repair manual. This usually involves additional visual inspections and multimeter tests of specific sensors and components related to the code you found. Follow the flowchart until the problem is pinpointed. At that point, replace or repair as needed.
