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2001 Mitsubishi Montero Limited P0300 Random Misfire: Causes and Troubleshooting Guide

Model: 2001 Mitsubishi Montero Limited Fault Code: P0300 Posted: 2016-04-10 18:09

I own a 2001 Mitsubishi Montero Limited with 113,000 miles. Since December 22, 2015, the vehicle has triggered a P0300 random misfire code five times. The issue consistently occurs during hard acceleration—such as when entering an interstate ramp—after approximately five minutes of driving. No other diagnostic trouble codes have been set. The car occasionally stumbles at idle. Spark plugs were last replaced at 60,000 miles and are now well beyond their recommended service interval. I am the original owner and have maintained the vehicle with regular care. I plan to replace the spark plugs and wires as a next step. What additional diagnostics or troubleshooting steps should I consider to resolve this issue?

Related fault codes

P0300

Comments (5)

Anonymous 2016-04-10 18:55

A random misfire like P0300 can be caused by fuel system issues, such as a clogged fuel filter or air filter, worn spark plugs, or a blocked catalytic converter. While replacing spark plugs is a common step, it's important to also inspect the fuel delivery, intake system, and vacuum lines for leaks. Additionally, check for coolant leaks—water in the engine can interfere with electrical components. If available, use an OBD2 scan tool to monitor fuel trims, oxygen sensor readings, and engine temperature or TPS voltage for deeper insights.

Anonymous 2016-05-07 07:17

I've been logging fuel trim and oxygen sensor data over several months. Both banks show a long-term fuel trim (Ltft) of around 12.5, with no drop below 10 even during hard acceleration. All four O2 sensors oscillate between 0 and 0.96, which is within normal range. Short-term fuel trims (Stft) fluctuate between -15 and +15 on both banks. The only code ever recorded is P0300, which appears exclusively during very aggressive acceleration—specifically when entering highways—and typically occurs just after five minutes of steady driving. The vehicle runs fine under normal conditions except for occasional idle stumbles. As the original owner, I notice a slight loss in power. The last major service was a timing belt replacement in October 2015, and the misfire began about 11 weeks later.

Anonymous 2016-05-07 13:15

The symptoms point strongly toward a fuel supply or injector issue, though worn spark plugs or ignition system faults should not be ruled out. A thorough inspection of fuel pressure, injector performance, and individual cylinder response is recommended to isolate the root cause.

Anonymous 2017-08-17 16:47

I tested for spark at the center coil and found none. After replacing the coil, no spark was detected either. What should I check next? Could it be a faulty wiring harness or engine control module (ECM)?

Anonymous 2017-08-17 17:10

http://www.revbase.com/BBBMotor/Wd/DownloadPdf?id=72733