2002 Chevrolet Monte Carlo SS P0300 Random Misfire Diagnosis and Repair Guidance
Hi, I own a 2002 Chevrolet Monte Carlo SS and am experiencing repeated stalling issues while driving on the highway. The car will stall, then only restart when placed in neutral—this has happened three to four times before it fails to start altogether. It turns over but does not ignite. Previously, I've had electrical problems including intermittent antitheft alarms that trigger without warning. I reset both the anti-theft system and the engine control module (ECM). A mechanic previously identified loose wiring connections in several connectors, which allowed me to get the car running temporarily. However, after a 100-mile trip, it stalled again upon returning home. I've now connected an OBD-II scanner and received code P0300—indicating a random misfire across cylinders. I have replaced the spark plugs and ignition wires with new Delco AC units, but the issue persists. I'm unsure where to focus my next steps for repair. Can anyone provide guidance on diagnosing and fixing this recurring P0300 misfire? What other components should I check—such as fuel pressure or sensor readings—to resolve this issue? Note: The term 'air code 0300' is incorrect; OBD-II codes use the prefix P0300 for random misfires. All relevant diagnostic codes should be referenced using the standard P0300 format.
Will your OBD-II scanner read all relevant codes, especially manufacturer-specific ones? Basic or low-end code readers often lack accuracy and may miss critical diagnostics. You mentioned replacing the spark plugs with new Delco AC units—have you confirmed that the plugs are actually firing properly? I recommend checking fuel pressure using a gauge (in PSI) to rule out fuel delivery issues. The term 'air code 0300' is not valid in OBD-II standards; P0300 is the correct prefix for random misfire codes. Always use standardized code prefixes like P0300, as other prefixes such as B0300 or C0300 are not recognized in official OBD-II systems. This ensures accurate diagnosis and repair recommendations.