1997 Monte Carlo 3.1L V6 - Persistent P0341 and P0336 Error Codes After Sensor & Fuel Pump Replacements
I own a 1997 Monte Carlo with a 3.1L V6 engine. The car began exhibiting severe jerking while driving, then suddenly stalled and would not restart. My uncle diagnosed the issue as a faulty camshaft position sensor, which was replaced due to being soaked in oil and coolant. However, the vehicle still wouldn't run for more than 10 minutes after that repair. He subsequently replaced both the crankshaft position sensor and the harmonic balancer, and also installed a brand-new fuel pump. Despite these efforts, the car continues to show persistent OBD2 error codes: P0341 and P0-336. These codes reappear every time we clear them using an OBD2 scanner. I recently had a baby and have limited financial resources—my mechanic is now at his wits' end, and I'm running out of both time and money. The engine has been thoroughly inspected, and all parts listed in the diagnostic process have been replaced. I'm seeking advice on what else could be causing these persistent codes or whether there's a deeper underlying issue. Could it be related to coolant leaks entering the intake manifold? In 3.1L V6 engines, coolant intrusion can lead to internal combustion issues and catalytic converter plugging. Symptoms may include slow acceleration, overheating, difficulty cranking, unusual exhaust smells, or increased fuel consumption—any of which could manifest simultaneously. Any insights into potential root causes or troubleshooting steps would be greatly appreciated.
That oil and coolant contamination in the engine is concerning. While your 1997 Monte Carlo may not have the same issues as a 3.4L Grand Prix, it's still possible for such leaks to cause serious internal damage. I recommend starting with a comprehensive engine cleaning using a high-quality degreaser. Remove the spark plugs and use carburetor cleaner to flush out built-up gunk from the combustion chambers. Also inspect the main spark plug connector located on top of the engine—perform a continuity test to check for broken or corroded wires, as vibration and thermal cycling can cause these failures. Once cleaned, apply a small amount of dielectric grease to each spark plug connection to prevent moisture ingress and contamination. Ensure that all wiring harnesses are properly routed away from hot surfaces and moving components. As a preventive measure, periodically hosing down the engine to keep it clean and free of debris can help reduce performance glitches. If there's a coolant leak—especially in the intake manifold area—it could be entering the combustion chamber. Coolant burned during combustion will produce exhaust fumes that may smell like rotten eggs or have a sweet odor, and it can lead to catalytic converter clogging. Symptoms such as hard starting, poor acceleration, overheating, and increased fuel consumption are all possible indicators. I hope this helps you identify the root cause before further costly repairs.