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P0300, P0131, and P0101 Diagnostic Issues on 1999 Pontiac Montana Van

Model: 99 montana Fault Code: P0101 Posted: 2007-05-13 12:05

I own a 1999 Pontiac Montana van and have recently started experiencing multiple OBD-II diagnostic codes: P0300 (random misfire), P0131 (oxygen sensor malfunction), and P0101 (mass air flow sensor range/performance issue). Initially, I replaced the camshaft position sensor, which resolved a temporary issue. After driving approximately 20 miles, random misfire codes reappeared. I applied Lucas fuel additive, which temporarily improved performance. After relocating from Maine to Florida, these issues have returned more frequently. I'm wondering if differences in local fuel quality or additives—such as ethanol content or oxygenate levels—could be contributing factors. While the vehicle has run smoothly for some time, last night it triggered all three codes again. I plan to reapply Lucas fuel additive and clear the codes to monitor any improvement. My main question: Could these symptoms be directly linked to changes in fuel composition in Florida compared to Maine? Any insights on whether fuel quality or additives play a role in triggering these specific engine codes would be greatly appreciated.

Related fault codes
P0101P0131P0300
Comments (3)
Anonymous 2007-05-14 05:21

Update: I re-added Lucas fuel additive, and the vehicle is now running smoothly again. Is this simply masking the underlying issue, or could it be genuinely improving combustion efficiency?

Anonymous 2007-05-14 06:57

Check the fuel pressure—low or inconsistent fuel pressure can trigger misfire and sensor-related codes like P0300 and P0101.

Anonymous 2007-05-14 07:46

The P0101 code is particularly concerning as it indicates a mass air flow (MAF) sensor range issue. While clogged exhaust systems can cause this, you also have random misfire codes, which suggests a more complex problem. To diagnose whether the MAF or exhaust system is at fault: unplug the MAF sensor and observe driving behavior. If performance improves, the MAF is likely faulty. If no improvement occurs (which I suspect), then check for backpressure in the exhaust system—obstructions can cause misfires and trigger multiple codes.