Dave_997

My 2012 Cayenne S, with around 146k miles, went from running sweetly to sounding like a tractor in the space of the 15 minutes it took me to pick up something from the store. Extremely rough running at idle and zero power with gas. I limped it home as I was close (may not have been wise) and there it has sat while I try and fix the problem. It sounds like the issue is with bank 2 (driver side), but it's not clear based on the codes (Durametric).

P1346
Valve lift control, bank 1
Implausible signal

P1347
Valve lift control, bank 2
Implausible signal

P0020
Intake camshaft position actuator circuit, bank 2
No signal/communication

P2088
Intake camshaft position actuator circuit, bank 1
Value below lower limit value

Based on this, my assumption was that one of the two VVT solenoids had stopped working (valve lift solenoid 94810530803 or valve timing solenoid: 94810530407). I'd previously replaced the lift solenoid on the back of the engine (firewall) on bank 1 and figured I'd do the same on bank 2, dispite the bank 1 codes, given (a) the noise appears to come from bank 2, (b) the lift solenoid on the back of the engine is far easier and cheaper to replace than the one under the valve cover, and (c) I'd already replaced bank 1 and it seemed unlikely to have failed again. This made no difference, so I bit the bullet and replaced the timing solenoid under the valve cover, also on bank 2. After reassembling everything I crossed my fingers and......no change.

I know people say bad mechanics just replace parts until it's fixed, but I really felt it had to be one of these two VVT solenoids. Of course it doesn't rule out an electrical issue with the cable/connector to either valve, but there wasn't anything obvious in terms of damage/corrosion to the connectors or frayed wires (although hard to be sure for the one on the back of the engine given the limited access). I do know that when the bank 1 life solenoid failed the symptoms were very different; it ran fine at higher rpm, but pretty rough at idle and stalled unless it was given some gas. If it is related to one of the VVT solenoids then this would lead to me to believe it's the one I just replaced under the valve cover. Both solenoids were new Porsche parts so it seems unlikely it could be the solenoid itself. I also checked the variocam bolts while I was in there and I don't have the type subject to the recall.

Any thoughts as to what to try next, or some insight into what could cause this rough running and generate codes on both banks?

I also uploaded a video of the engine running to youtube in case this helps with diagnosis. You'll see I pulled the connectors on each bank 2 cyclinder in turn and the engine ran more lumpy each time so I don't think it's to do with the ignition system:

AnAlbumCover

P0020
Intake camshaft position actuator circuit, bank 2
No signal/communication

This leads me to think your camshaft position sensor went bad? Bad sensor may throw off all those other values....or the car skipped time

Dave_997

Thanks AnAlbumCover!

I didn't consider that and it's an easy thing to change given it's position on top of the bank 2 valve cover....the question is, do I dump another $100 to find out!

AnAlbumCover

maybe just try cleaning out the plug or unplugging completely and seeing what codes you get? Or, bite the $100 bullet, not a lot in the grand scheme.

Dave_997

Agreed, what's another $100 in the scheme of things! I see FCP have the Bosch part for $56 so probably worth it even to rule it out!

wyowolf

Timing chain guides? that would cause it as well...

garrett376

Yes, my bet is your timing chain guides disintegrated and need replacement.

garrett376

https://rennlist.com/forums/cayenne-...r-of-time.html

Dave_997

Thanks guys, that would be bad…. Is there a way of inspecting/confirming that doesn’t require the timing cover to be removed? I didn’t see any evidence of broken plastic under the valve cover and the fact that this happened suddenly would suggest a major failure if it were the guides. Would I not see some broken plastic transported up by the chain?

wyowolf

They can partially fail, on my 540i thats what happened, the lower guide cam apart, not enough to damage anything but I was defiantly running rough...

Dave_997

I took a look at the post that garrett376 linked (by Bob958S) on this subject which was really helpful in understanding the nature of the failure. Doing some more digging it seems it's the u-shaped inner guide that desintergrates and the pieces typically make their way up into bank 2 and bunch up behind the first sproket and the casing. Annoyingly I've already put the bank 2 valve cover back on, but checking the photos I took I don't see any evidence of this happening. Obviously it would be nice to be able to shine a flashlight down there to see if it's still in place. I also have a cheap borescope that would be useful in getting down in there from the valve block without taking the timing cover off, so maybe that is the next step. But I don't have the P0016 or P0344 codes that appear to be associated with this.....

Just read the rest of the Bob958S thread and realized it's possible to check the guide using a borescope inserted via the oil cap on bank 1. I'll see if I can make this work and report back. It doesn seem that this is likely the cause given the age/miles. Funny, I've just bought a 2019 S and was getting the 2012 ready for sale when this happened - but maybe the fact it happened to me rather than some poor guy excited about his new car gets me a karma credit for future use!

Dave_997

You can't reach much from oil cap, but I can see the top of the guide still in place on the bank 1 side and a length of guide disappearing downwards. Also, I don't see any pieces of broken plastic elsewhere within the bank 1 side of the cover. I may poke around some more, but it appears that the cover limits how far down I can extend the scope. I know it doesn't necessarily mean it's not broken out of sight, but so far I'm not seeing the signs that others have experienced for this type of failure





Looking at edge of guide from under chain

looking down on guide from top where it curls around bracket

Showing the u-shaped inner guide in black, mine appears to be brown like the small guides seen between sprockets

Dave_997

I realized I could check the cam deviation using a scan tool as an indicator of a problem with the chain/guides. From reading, +/-2 deg is great, +/-5 deg is fine and >10 deg is a problem. The deviation on bank 1 is 2.25 deg and -0.75 on bank 2. The camshaft angle for both banks matched the setpoint of 130 deg. I also checked the voltage to, and resistance of, the timing solenoids and cam sensors between bank 1 and bank 2 and they give the same values. Not possible to do same for the lift solenoids given the limited access. Based on this, it doesn't seem to me that cams or timing is the issue; not sure if my troubleshooting logic is sound though?!

Appreciate any other suggestions as to what could be going on. And when I say rough running, I mean so rough I'm scared to start it, it sounds that bad. Something more fundamental in the engine?

At this point I think I probably need to trailer it to a mechanic to diagnose - at least I now have a 2019 to tow the 2012.

wyowolf

Well given the values it seems you can rule that out, which is good. ON my 540 it was the U that failed... hope you get it figured out. To be running so rough is troubling...

Dave_997

Wyowolf - thank you, I appreciate you taking the time to comment!

For anyone else interested, I'll post an update when I figure out the issue.