2011 GMC Tahoe Hybrid P0307 Misfire: After Replacing Coils, Wires, Plugs & Injectors Still Persistent
I own a 2011 GMC Tahoe Hybrid with approximately 67,000 miles. About a month ago, the vehicle displayed the message 'ENGINE POWER REDUCED, SERVICE STABILTRAK, ETC.' The engine appeared to run normally at first, so I turned it off immediately and attempted to retrieve diagnostic codes using a code reader. When I restarted the vehicle, no codes were detected. I took it for a drive—everything was fine with no warning messages or check engine light. A week later, my wife encountered the same message while driving, and the engine began running roughly. She pulled over and shut off the vehicle. I advised her to wait a few minutes in hopes that the issue would resolve itself, similar to what happened previously. However, this time it did not. The truck was eventually driven just one mile to get home, during which it ran poorly. After pulling codes, I received P0307—indicating a misfire in cylinder 7. I initially swapped the spark plug and wire from cylinder 5 to cylinder 7, which triggered a P0300 (random/multiple cylinder misfire), leading me to suspect a faulty coil on cylinder 7. I then replaced all spark plugs, ignition coils (excluding #6 and #8 due to access limitations), and distributor wires. Despite these replacements, the P0307 code persisted. I later researched online and concluded that fuel injectors could be the root cause. After installing new injectors—tested with a NOID light prior to installation—the issue remained unresolved. I also replaced both knock sensors and upgraded from an original 12V battery to a brand-new one. One month after all these repairs, the P0307 code still appears. The check engine light comes on and begins flashing, indicating potential catalytic converter damage. I have not driven it far—only enough to reach operating temperature and trigger the light after resetting. There are no unusual exhaust odors (no rotten eggs or coolant smells), and the vehicle runs roughly, especially when backing up in reverse. The idle is also rougher than while driving, though I’ve only pushed it to about 40 mph. The only remaining component not replaced is the throttle body and throttle position sensor—some forums suggest these can resolve 'REDACTED ENGINE POWER' issues—but I haven’t seen this message in nearly a month. I am now at an impasse and seeking advice from others who have encountered similar problems or any potential solutions. Any insights, experiences, or troubleshooting steps would be greatly appreciated!
Does your code reader support both generic (P0xxx) and manufacturer-specific codes (e.g., P1xxx)? Some basic scanners only read up to P0999. Is this vehicle equipped with Active Fuel Management (AFM), which is common in 2007–2011 GM V8 engines? Currently, the only code reported is P0307—any other codes or pending ones? What does cylinder #7 spark plug look like visually—wet, black, dry, tan? Are you using AC Delco parts (aftermarket components can sometimes cause issues)? For misfires, we typically investigate spark, fuel injection, vacuum leaks, and then perform a compression test. Can you confirm if the engine has AFM or V8 configuration?