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2003 Mitsubishi Diagnosing P0300 and P0660 After Fuel Assembly Replacement

Model: 2003 Mitsubishi Fault Code: P0300 Posted: 2018-07-01 18:37

Three months ago, I replaced the fuel assembly on my 2003 Mitsubishi due to a crack in the lid. Recently, without warning, my car suddenly lost power—now it will only go up to 20 miles per hour. The check engine light came on abruptly, not blinking, and this change happened in just a moment: one minute everything was fine, the next I was stuck at 20 mph. After pulling into AutoZone about a block from where this started, the vehicle displayed two diagnostic codes: P0300 and P0660. I've taken it to three different mechanics, each offering a different diagnosis. Instead of replacing parts randomly, is there any reliable way or expert insight that can help me accurately diagnose the root cause? I want a proper fix, not just a temporary patch.

Related fault codes
P0300P0660
Comments (3)
Anonymous 2018-07-01 19:07

Possible causes for P0660 in a 2003 Mitsubishi include: defective intake manifold runner tuning valve, broken or stuck valves, extreme cold conditions, wiring issues (such as chafed, cracked, or corroded connections), faulty electrical connectors, ECM problems, or valve contamination. For accurate diagnosis, it's essential to verify each component systematically. Read more: p0660 diagnostic guide. Always choose a mechanic who provides clear explanations and stands behind their diagnosis to avoid unnecessary part replacements.

Anonymous 2018-07-01 19:20

I'm in Fort Worth and have been looking for a trusted mechanic—some shops seem to treat me differently, as if I'm not a regular customer or may be overpaying. Any recommendations for reliable auto repair services in the area?

Anonymous 2018-07-02 09:45

Consider reviewing mechanic evaluation reports from Cartalk.com—they offer real-world insights and case studies that can help identify common issues with older vehicles like the 2003 Mitsubishi. To avoid overpaying, prioritize a technician who is confident in their diagnosis and offers a warranty or follow-up if the issue returns.