2003 Chevrolet Trailblazer 4.2L Engine Misfire and P1345/P0300 Codes - Help with Check Engine Light, Shaking, and White Smoke
Hi everyone, I have a 2003 Chevrolet Trailblazer 4.2L with an idle issue that has worsened after several repairs. The truck started misfiring and I initially cleaned the throttle body (it's at 160,000 miles). I then replaced the fuel filter, spark plugs, and oil filter. After these changes, the problem actually got worse. The vehicle now shows check engine codes: P1345, P0300, and P0014. I recently installed a new variable valve timing solenoid, camshaft position sensor, and crankshaft position sensor. I also changed the engine oil. Initially, there was only a slight noise suggesting timing issues were out of sync. I drove it home about one mile when the check engine light came on and began blinking. The 'Reduced Engine Power' warning lit up, and the truck started shaking severely—producing loud bangs. It lost acceleration: RPMs would rise but not increase, then stalled. After letting it sit for a few minutes, I tried restarting it again and heard another loud bang with a significant amount of white smoke coming from the exhaust before stalling once more. I haven't been able to start it since. I'm looking for advice on what might be causing this—especially given the combination of misfire codes, engine shaking, and white smoke. Any insights would be greatly appreciated.
Multiple issues are present here. This is a straight-6 engine (4.2L inline-six), so it's important to confirm that. Key points to consider: 1. As a precaution, check the engine oil for signs of fuel contamination—this could indicate a serious internal issue or fuel system malfunction. 2. The P0300 code appeared only after replacing spark plugs—this suggests the misfire may not be directly related to plug wear but possibly due to electrical connections or component compatibility. >>> Check all spark plug wiring, coil connectors, and coil boots for loose or damaged connections. Some brands of spark plugs (like AC Delco) have been known to cause intermittent misfires; Bosch plugs are generally more reliable in this application. 3. You replaced both the crankshaft position sensor (CKP) and camshaft position sensor (CMP). >>> Did you perform a CKP relearn procedure after installation? This is critical for proper engine timing and ignition control, especially after replacing sensors. These steps may help identify or resolve the root cause of the misfire and stalling issues.