2001 Mitsubishi Eclipse Spyder GT P0301 Misfire: Causes, Fixes & DIY Diagnosis
I own a 2001 Mitsubishi Eclipse Spyder GT with a 3.0L V6 engine and over 10,300 miles. About a week ago, I switched from regular to premium fuel, and two days later my car began exhibiting unusual behavior — it would sputter and feel like it was running on only five cylinders under all driving conditions: low RPMs, high RPMs, or under load. I recently replaced the spark plugs, ignition wires, and coils. After these changes, the misfire issue persists intermittently. The car now throws a persistent P0301 code (misfire in cylinder 1), though I've noticed that after clearing it with my scanner, the symptom appears only when accelerating to 5,000–7,000 RPMs — a behavior not present before. The engine idles smoothly and runs fine at low speeds. However, under load or during acceleration, it sputters intermittently, sometimes lasting for seconds, other times disappearing entirely. The car previously ran rich; now it runs cleaner, but the P030-1 code remains. I’ve ruled out common issues: no noticeable exhaust smell, catalytic converter is functioning properly, and I recently replaced the engine control module (ECM). I don’t see how an O2 sensor would cause a misfire without triggering another diagnostic code. The problem doesn't seem to be in fuel delivery or air intake. I’m wondering if the issue could stem from the distributor or rotor cap — especially since these components are common in older V6 engines like mine. However, I’ve already replaced plugs and wires, so is this a case of faulty ignition timing or sensor failure? Could it be related to the camshaft position sensor? I’ve heard that misfires at high RPMs can sometimes point to timing-related issues. I’m looking for reliable, factual input from experienced Eclipse owners — no guesswork. I don’t want to spend money on unnecessary parts. Any advice or diagnostics would be greatly appreciated.
Hi, I have a similar issue with my 2001 Mitsubishi Eclipse G3 3.0L. I replaced the spark plugs, wires, distributor cap, and rotor — but the problem persisted. Two days later, I checked the timing belt markers on both the crankshaft and camshaft — they were aligned correctly. After five days of no improvement, I replaced the distributor assembly. Unfortunately, that didn’t resolve the issue. I then took it to a workshop where they installed a new camshaft position sensor. After reinstallation, I turned on the ignition and confirmed the warning light went off. Using an OBD2 scanner, no diagnostic codes were present. Since then, the sputtering and misfire have completely disappeared. This experience suggests that a faulty camshaft position sensor can cause intermittent P0301-like symptoms, especially under load or at higher RPMs. I recommend checking this component on your Eclipse Spyder GT — it’s a common but often overlooked fix for V6 engine misfires.