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2002 Chevrolet 5.3L VIN T - P0171, P0174, P0300: Lean Bank 1/2 & Misfire Issues | Cold Start Rough Idle

Model: 02 Chevy 5.3L Fault Code: P0171 Posted: 2007-03-14 21:36

Help needed: Check Engine Light is on with fault codes P0171 (Lean Bank 1), P0174 (Lean Bank 2), and P0300 (Multiple Misfires). The vehicle exhibits a rough idle for approximately 4 seconds after a cold start. Performance improves when RPM is maintained around 1200. Once the engine reaches normal operating temperature (195°F+), it runs smoothly. I've already inspected the air duct and cleaned the Mass Air Flow (MAF) sensor using an electric parts cleaner—no improvement was observed. I confirm a stable 5V reference signal at both the MAF and water temperature sensor. Oxygen sensors appear functional, wiring is intact, and new spark plugs and a Fram air filter have been installed. The engine has approximately 42,000 miles total (the rest of the mileage was driven while towed behind a motorhome). I'm seeking advice on next steps to resolve this issue. Any insights would be greatly appreciated.

Related fault codes
P0171P0174P0300
Comments (3)
Anonymous 2007-03-16 08:23

Check fuel pressure and inspect intake gaskets for leaks. These are common causes of lean conditions and misfires in the 2002 Chevrolet 5.3L engine.

Anonymous 2007-03-16 09:19

What happens when you disconnect the MAF sensor? This can help determine if the MAF is contributing to the lean readings or misfire symptoms.

Anonymous 2007-03-20 08:41

First, thanks for the helpful suggestion. I disconnected the MAF and restarted the engine—it ran smoothly with RPM rising slightly to about 700–750. After turning off the engine and reconnecting the MAF, it returned to a rough idle. I then replaced the MAF with a new AC Delco unit. After several starts, the Check Engine Light turned off and overall performance improved significantly. However, there's still a very slight idle stumble without any SES light active. As a next step, I plan to replace the fuel filter cap and fuel pump rotor. Spark plugs were already replaced earlier.