P0302 Diagnostic: 2003 Toyota Tacoma 4Cyl 2.4L - Misfire in Cylinder #2 with Intermittent Code Set
2003 Toyota Tacoma, 4-cylinder, 2.4L engine, regular cab, 2WD, automatic transmission, 196,000 miles. The P0302 diagnostic trouble code appears intermittently — sometimes setting within a single 50-mile drive and other times not appearing for up to a week. There is no clear pattern in when the check engine light comes on. While the vehicle occasionally runs roughly, this roughness does not coincide with the appearance of the P0302 code; instead, it typically occurs hours or days after the code appears. The code has been observed both before I back out of the garage and after driving for nearly an hour. Fuel economy remains consistent. I have already replaced the oxygen sensor, spark plugs, and the coil pack specifically for cylinder #2. All spark plugs appeared clean during inspection. Compression test on cylinder #2 reads approximately 150 psi. Freeze frame data from several P0302 events shows: - Fuel System 1: CL (Controlled) - Fuel System 2: CL-Fault - Calculated Load (%): 80.78% - Engine Coolant Temperature (ECT): 186°F - Stoichiometric Fuel Trim B1 (%): +0.78% - Lift B1 (%): +3.13% - Engine RPM: 1967 - Vehicle Speed (mph): 3 - Air Intake Temp (IAT): 107°F Another event: - Fuel System 1: CL - Fuel System 2: CL-Fault - Calculated Load (%): 84.31% - ECT: 159°F - STFT B1 (%): +0.78% - LIFT B1 (%): +1.56% - Engine RPM: 2500 - Vehicle Speed (mph): 10 - IAT: 68°F Final event: - Fuel System 1: CL - Fuel System 2: CL-Fault - Calculated Load (%): 42.35% - ECT: 95°F - STFT B1 (%): -0.78% - LIFT B1 (%): 0% - Engine RPM: 970 - Vehicle Speed (mph): 3 - IAT: 82°F Fuel trim values are relatively stable, with only minor fluctuations in stoichiometric trim and lift, suggesting no significant fuel control issues. However, the intermittent nature of the P0302 code indicates a potential underlying mechanical or electrical issue. Next steps include testing for cylinder leakage using a leak-down test to assess mechanical integrity, checking for vacuum leaks, and considering a swap of the #2 injector with another cylinder in the fuel rail to determine if the misfire relocates. If the code persists after these checks, further diagnostics may be required.
Try swapping the #2 fuel injector with one from another cylinder on the fuel rail to see if the P0302 code moves to a different cylinder. If the code stays in cylinder #2 after the swap, it points to an internal mechanical issue such as worn piston rings or valve problems. If the misfire shifts to another cylinder, then the problem is likely with the injector itself. Additionally, perform a cylinder leakage test to evaluate mechanical integrity and check for vacuum leaks — though fuel trim data does not indicate major fuel control issues. Good luck, and please update us on your findings and progress.