2003 Nissan Altima Misfire Diagnosis
In this How-to, I'll show you how I diagnosed a check engine light caused by a misfire on a 03 Altima. The DTC was P0304: Cylinder 4 misfire detected.
Most misfires are ignition-related. In this case, I was able to diagnose a faulty ignition coil causing the misfire.
TOOLS REQUIRED:
-OBD2 code reader
-5mm hex bit socket or key
-10 mm socket
-ratchet
-sparkplug socket
-extension
ESTIMATED TIME:
20-30 minutes
STEP 1: Connect the code reader to the OBD2 port, located underneath the steering wheel. Turn the ignition on.
STEP 2: If your car has a P0301, P0302, P0303 or P0304 code, this process will be the same. Open the hood by releasing the hood latch, located left of the OBD2 port.
STEP 3: Remove the engine cover by taking out 4 5mm hex bolts
STEP 4: Identify the correct ignition coil for the misfiring cylinder in this picture. In this case, I was working on cylinder 4.
STEP 5: Disconnect the electrical connection on the ignition coil, and remove the 10mm bolt holding it down. To identify a faulty ignition coil, I marked an x on the coil, and swapped the coil with another cylinder, cleared the trouble code and drove the vehicle. This misfire code returned, but this time It changed to P0303 cylinder 3 misfire detected. This happened because I swapped the suspected faulty coil with cylinder 3.
STEP 6: If you swapped the ignition coil and the misfire followed to the cylinder you swapped to, this identifies a faulty ignition coil. Replace the ignition coil. While you have the coil removed, it's probably a good time to inspect your sparkplugs if you've never done a tune-up to your engine before.
STEP 7: Put everything back together, close the hood. Remember to clear the DTC.
Job done!
