Bad cold engine knocking

[remi34000]

Originally Posted by dpaul

Noise going away after the engine warms is a classic symptom of piston slap.
Piston slap is the result of too much clearance between the pistons and cylinder bores and is most evident when starting a cold engine because that's when the clearances are greatest.

That said, it is not necessarily pathological. Many engines exhibit this behavior when new. When the noise persists after warm up, that's when you should start to worry.

In addition, it is unclear to me how piston slap would result in abnormal VANOS activity. Further, the fact that you sometimes don't hear it on startup is inconsistent with piston slap which should occur every time - if the engine is cold. Finally, your noise goes away very quickly - too quickly to ascribe to piston slap (in my limited experience).

Your noises could indicate many different kinds of problems and as has been pointed out, it is usually a fruitless endeavor to diagnose a problem based on a YouTube presentation of sounds recorded on a cell phone

I'll repeat myself; if you really want help, start by listing all the error codes that ISTA or INPA report.

Thank you for your very complete answer, what you are explaining may be true but in this case I cannot understand why it does not do it all the time, sometimes loud, sometimes not loud and for a longer or shorter time. Seems too irregular for a piston problem. It does not issue a fault code, except once I found cyl 5 and 6 misfire. But after deleting the codes it did not come back. I'll take off the cylinder head cover to look and put a camera through the spark plug.

[dpaul]

OK, let us know what you find.

[remi34000]

Originally Posted by dpaul

Noise going away after the engine warms is a classic symptom of piston slap.
Piston slap is the result of too much clearance between the pistons and cylinder bores and is most evident when starting a cold engine because that's when the clearances are greatest.

That said, it is not necessarily pathological. Many engines exhibit this behavior when new. When the noise persists after warm up, that's when you should start to worry.

In addition, it is unclear to me how piston slap would result in abnormal VANOS activity. Further, the fact that you sometimes don't hear it on startup is inconsistent with piston slap which should occur every time - if the engine is cold. Finally, your noise goes away very quickly - too quickly to ascribe to piston slap (in my limited experience).

Your noises could indicate many different kinds of problems and as has been pointed out, it is usually a fruitless endeavor to diagnose a problem based on a YouTube presentation of sounds recorded on a cell phone

I'll repeat myself; if you really want help, start by listing all the error codes that ISTA or INPA report.

I will also take the compression. Which sensor do you disconnect so that the injector does not work?

[remi34000]

I took the compressions they are correct and thanks to an endoscopic camera I could see that nothing is damaged. I'm going crazy