1. Verify the Diagnostic:
* Double-check the diagnostic: Was it a professional scan tool or a less sophisticated code reader? A professional scan tool can give more detailed information about the misfire (which cylinder, etc.). A generic code reader might only indicate a general misfire.
* Clear codes and retest: After cleaning the injectors, did you clear the trouble codes from the car's computer? The computer needs to be reset to see if the problem persists.
* Check for pending codes: Some scan tools show pending codes – these indicate problems the computer is *detecting* but hasn't yet flagged as a full-blown fault code.
2. Investigate Injector Issues Beyond Simple Cleaning:
* Injector flow test: A proper fuel injector flow test is crucial. Cleaning might not resolve issues like a clogged filter within the injector, a sticking injector, or inconsistent spray pattern. This requires a specialized tool to measure the flow rate of each injector. The flow rates should be similar across all injectors.
* Injector resistance test: Use a multimeter to measure the resistance of each injector. Resistance outside the manufacturer's specifications indicates a faulty injector.
* Injector wiring and connectors: Inspect the wiring harness and connectors going to the injectors for damage, corrosion, loose connections, or broken wires. A bad connection can mimic a faulty injector.
3. Explore Other Potential Causes (Even if the diagnostic pointed to injectors):
* Ignition system: A misfire can also be caused by problems in the ignition system. Check:
* Spark plugs: Inspect for wear, fouling, cracks, or damage. Replace them.
* Spark plug wires: Look for cracks, damage, or poor connections.
* Ignition coil(s): Test the ignition coil(s) for proper output. A faulty coil can cause a misfire in the cylinder(s) it controls.
* Ignition control module (ICM): This component controls the ignition system. A failing ICM can lead to multiple misfires.
* Air intake system: A vacuum leak can disrupt the air/fuel mixture, leading to a misfire. Inspect all hoses, connections, and the air filter for any issues.
* Mass airflow sensor (MAF sensor): A faulty MAF sensor provides inaccurate information to the computer about the air intake, causing incorrect fuel delivery.
* Crankshaft position sensor (CKP sensor): A malfunctioning CKP sensor can prevent accurate timing of the ignition system, leading to misfires.
* Fuel pressure: Check the fuel pressure to ensure it's within the manufacturer's specifications. Low fuel pressure can lead to a lean fuel mixture and misfires.
4. Professional Help:
If you're not comfortable performing these tests yourself, it's best to take the car to a qualified mechanic. They have the tools and expertise to diagnose the problem accurately and make the necessary repairs. Explaining you've already cleaned the injectors is crucial; it saves them time and you money on unnecessary work.
Remember safety first. Work on the car in a well-ventilated area and disconnect the negative battery terminal before performing any electrical tests.
