2001 GMC Yukon XL. When I start the engine, especially in cold temperatures, the engine knocks softly until it warms up for a few minutes.
Bad air/fuel mixture could cause rod knock like that, which is a for of backlash or whip like action. Detonation, like very poor grade of fuel. IF your engineis running really rich, the extra rich fuel goes by your piston rings and thins out your engine oil. If you have a bad ROD bearing, it is probably TOO LATE. CLEAN YOUR THROTTLE BODY and IAC valve, since these things fine tune your FUEL/AIR mixture and PREVENT rich running. GOOD LUCK!!
SOURCE: My GMC yukon XL 2001 engine runs after 4 times of cranking.
Try turning key to on only, not start, 2 or 3 times first then try to start. If it starts good first try, then I'd change my fuel filter & then have fuel pressure tested if fuel filter didn't help. You may be looking at a new pump, but lets do filter & test fuel pressure first.
SOURCE: i have an engine code PO332 knock sensor 2 circuit
The most likely cause of your code is a bad rear knock sensor. You should check the knock sensor wiring harness for corrosion. But if that checks out the sensor will have to be replaced. The knock sensor is under the intake manifold, although it's not too difficult to remove. Both knock sensors should be replaced along with the wiring harness, just because of labor involved in gaining access to the sensors. You could try clearing the code, it may stay off for a long time.
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6.2 gas engines had a piston knock when cold
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