Question about 2003 GMC Yukon XL

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2003 Yukon. The engine light kept staying on. Changed all 4 02 sensors, all spark plugs. All spark plug wires. Now engine light is off and it runs smooth except every three or four days, I will start it up after not running for a few hours and the motor runs very rough and does that for a while. i check it with a diagnostic, it says mutliple misfires, code PO300. Then I erase the code. Then strangely the engine runs smooth. it does that for a few days and then same problem again. I'm stumped.

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Replace the fuel pressure regulator.

Posted on Jan 25, 2011

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If you replaced the plugs, did you replace the plug wires. Even though they are short wires from the coil to the plugs they can go bad. How is the air filter? Have you replaced the fuel filter?

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If you change the sensors, your pcm (vehicle computer) will detect the change in readings very quickly. If you really want to ensure the computer completely relearns you need to disconnect the ground for at least 10-30 minutes. When you reconnect the battery the computer will return to its baseline from the factory. It will immediate begin the adaptive learning process to perform in accordance with your driving style.

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not at all and when changing your spark plug there is no reason not changing the spark plug wires too..

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