P0021 and Noises

[jbahrami]

​​Hello,

I have a 996tt which is making knocking/rough sounds at idle and while driving. The noise seems to change with the RPM, however, it goes away depending on the engine load.

Here is the information I have gathered so far:

- Durametric shows code P0021 - Porsche fault code 325 - Camshaft position with respect to crankshaft bank 2.

From what I have read it seems like this could be caused by a “spun cam” where the inner sleeve of an intake cam rotates, blocking oil flow used to advance the camshaft. Some details here ​​https://www.joeleggs.com/blog/997-turbo-gt2-camshaft-adjustment-failure-fault-code-p0021

- Camshafts deviation for bank 2 is ~13 degrees, while bank 1 is near 0.

- Occasionally code seen these codes, however, they have not persisted:
P1349 - Camshaft adjustment bank 1 Below limit
P1358 - Camshaft adjustment bank 2 Below limit

- When I activate the variable lifter with the Durmatric the idle becomes rough and there is a clunking sound.


I am preparing to open camshafts in December, but ahead of this, I want to anticipate what I might encounter.

Any thoughts on what could be going on?

Thank you!

[JFP in PA]

The cam sleeve has probably moved, partially blocking the oil passage.

[jbahrami]

I wanted to provide an update on this thread. I have narrowed down the issue I described above to likely be caused by timing gear separation from the intermediate shaft. I can discuss how I narrowed it down to this if anyone is interested, but I have eliminated the possibility of failed lifters, spun cam sleeves, worn oil control rings and housings, defective cam phasers, defective solenoids, worn chain guides, stretched chains, and failed chain tensioners.

Timing gear separations are apparently a rare occurrence, but it happens when the bolts holding the timing gear to the intermediate shaft come loose. This issue is possible on most Mezger engines, but so far have only seen this discussed on 996TTs. See these links where other people have documented this same issue.

Here is a photo I found of this same issue taken from the link below:
http://www.911uk.com/files/p4121363_874.jpg

911uk.com - Porsche Forum : View topic - 996 turbo IMS failure

https://www.pistonheads.com/gassing/topic.asp?t=1121214

Similar to what was described in the above links, the rattling is most prominent when the engine is decelerating from around 3k on down, and when the intake cam high lift is activated.

Unfortunately, the solution for this requires an engine teardown and rebuild to replace the intermediate shaft and gear use good Loctite on the retaining bolts. A better and more expensive alternative is to use the intermediate gear set from the GT3, which is a one-piece part.

In my case, I will eventually have to dismantle my motor to confirm my suspicions. For now, the car will not be driven.

Has anyone else encountered this issue on their 996TT/997TT motors or any air-cooled motors, and could you please contribute your experience here?

Thank you,
Jeff

[jbahrami]

Hello,

I just wanted to provide closure to this post. I have successfully resolved the issues I described above, and thankfully, they were not related to the timing gear. Please refer to my update in this thread for further details - Cam Position Deviation on 996TT