Help with a P0021 please

[Zakowsky]

Hi all,

I used to contribute a lot here regarding the Cayenne TT, but I haven't posted in years - my Cayenne Turbo went the way of all things and now I have a 997.1 TT to fill my time.

I am really at an impasse now, and as I saw some threads regarding the P0021 situation here I was hoping Loren or JFP or anyone might have some experience with something like this. I had a P0021 with the Signal Implausible clause (read from a PIWIS 2) after a 3-4 shift at WOT with a puff of black smoke out the back. Sure enough Bank 2 did not respond any more to throttle blips.



I replace both actuator solenoids, and the solenoids and actuators seem to be working now.



But after driving for a while I would see the offset between the 2 banks jump all of a sudden, and bank 2 occasionally not track bank 1

 

If I stop logging and reset the PIWIS they start moving in sync again! Which I thought might be the PIWIS, but the P0021 comes right back when this happens, so it seems real.

So I was previously worried obviously about spun cam sleeves, but if the solenoids and the actuators are working, then that seems less likely. I am at a loss for what to try next, the only things I can think of are

1) Camshaft position sensor is faulty - but that should generate a different error code, shouldn't it (like P0343 for bank 1)?

2) The camshaft has jumped a tooth - but then wouldn't the offset always be the same?

3) Something is sticking inside the Bank 2 actuator.

To note, when I replace the solenoids, I found that the Bank 2 solenoid had not been installed properly, so it is possible it had had compromised function for some time. So maybe the bank 2 actuator works to adjust, but the base offset gets stuck? I am not sure how the actuator is designed.

Any ideas would be appreciated, before I resign myself to tearing this all apart. Thanks,

Mike

 

[Loren]

P0021

 

Possible fault causes
- Dynamic driving style when oil level is near minimum (oil foaming)
- Solenoid hydraulic valve faulty
=> (e.g. mechanical fault or dirt in the oil circuit)
- Oil pressure too low
=> (e.g. due to oil dilution, oil thickening, wrong oil quality, fault in oil pressure control or oil pump)
- Intake camshaft adjuster faulty
- Camshaft stuck (incorrect or faulty installation)

[Zakowsky]

Thanks Loren,

I have read through all the documentation on this, and scoured the online resources. Just wondering if anyone has seen these kinds of logs before - I believe the variocam works by the oil pressure from the holes in the camshaft sleeve shifting the helical gear in the adjuster one way, and the oil from the solenoid pushing it back the other. So since the timing shifts both ways fine, it seems these circuits are OK. So the only way this could be the variocam is if maybe the bolt that holds it on the cam shaft is loose maybe? And that causes the offset to come and go? That would mean it would be bad to even run the engine, I would think. But you would think there is a pin or something to hold the variocam to the camshaft...thanks.

[Loren]

Or... the bracket that hold the solenoid is cracked. That happened on 996TT a few times.

[Zakowsky]

Interesting, thanks Loren. I believe the 996TT uses a slightly different mounting system than the 997TT, but the idea that this could play a role is something for me to check.

I feel pretty dumb, but I figured out the shift - I had no idea the PIWIS auto scaled each trace separately - duh. So they are in fact not shifted. But unfortunately I still get the P0021 coming right back. I think the problem is that although it tracks most of the time, there are times that Bank 2 just doesn't respond at all like Bank 1 - so in that graph like at the arrows.


Looks like the variocam is sticking sometimes. Is there any oil "flush" that is safe and useful for this engine? I used SeaFoam on my Jeep, but not on the Mezger...thanks.