Originally Posted by J'sWorld

No need to resurrect a thread from the dead. This post is about the v6 which is a totally different design. You have a 4.5 v8 and I told you advice on the thread you started. There are not many people with experience of the inner workings of the 4.5. I am one of the few here who do. The most probable failure to the degree that would cause a problem on this engine is the upper U guide or the tensioner itself. The tensioner guide is not large or curved enough to illicit a change in timing that the tensioner itself cannot compensate for. The chain does not stretch. The rollers/pins do not wear. The sprockets do not wear. Up to probably 250+ k miles on a properly maintained engine these items do not wear enough to illicit a change that cannot be compensated for by the variocam actuators or the tensioner.

I told you what to do in your thread you started. I will add one more thing and tell you why. Check the cam deviation from bank 1 to 2. Bank 2 is the driven side. It is almost physically impossible to develop slack between the crank and bank 2. This is not likely. The large upper u guide is between bank 1 and 2. This U guide is the most likely to fail due to the design and how much load it carries. If there is an issue with this guide you will see a large deviation between the two banks. The deviation is only measured at each intake cam because this engine only has intake cam position sensors, not exhaust. Even if you have a large deviation between the two banks the ECU can compensate to a point by adjusting the variocam actuators via the variocam solenoids to make both banks equal while the engine is running. There is a large margian of adjustment built into the design and it is not all needed. This is so that the actuators can adjust for wear and make the actual intake camshaft angles match while the engine is running at idle and still be able to achieve full intake camshaft advance at speed or when the ECU desires it. The ECU calculates deviation by looking at several measurements.

Now that I have given the technical explanation of something that you will not understand I will refer you to the original advice of compression test and borescope. The reason for this is because it sounds like you have a case of bore scoring developing. You need to explore this and eliminate it as a variable right now because it is the cheapest and most important diagnostic expense you will incur and it needs to happen first in the work flow due to costs. You have not given us enough information to take a more educated internet guess because you do not work on the vehicle. I have taken this into consideration.

Listen carefully-

Your mechanic is not qualified to work on your Cayenne anymore. He is telling you to sell because he cannot figure out the problem and does not want to admit that to you. It looks bad on his part. A true timing issue would be not only fixable but very profitable for him.

Eliminate or validate the possibility of bore scoring before you move forward. Fuel fouls plugs more with soot than with deposits as oil does in the short term. Fuel fouled plugs are not likely to misfire after the mixture is corrected. Oil fouled plugs will.

Originally Posted by Levitas Etan

I've got a 2006 cayenne s. 120k miles. Taking really good care of of it.
I live in Israel and there's just a few cayennes and fewer Porsche experts.
They are trying to sell me an engine!

My car is properly maintained.
Top spec oils, Cera tech etc.

A year ago.
We did valve cover gaskets due to leakage.
After that we did coils and plugs.

Lately we had some issues.
Alternator went bad so I sent it for refurbishment.
While waiting for it the battery went flat. It is a 5 month old bosch s5.
Recharged it for a few days and it came to life.
Later I got multiple CELs due to Crack shaft and 2 cam shaft position sensors.
Car was turning off spontaneously... So we replaced both cam and the crank shaft sensors.

It was fine.
For a week.

Since that week I have a constant CEL showing Bank 2 camshaft Position Sensor.
Replaced the sensor with a new one again.
Didn't help.

Mechanic told me that the timing chain jumped a little.
And that it's less expensive to replace the engine than do a timing job....

Just that weekend after the car sat for 3 days.
I wanted to take it for a ride.
When starting the car no CEL. Drives normally.
It was fine.

3 days later... Same CEL again...

I use Carsoft por ii to erase the CEL but it comes back again...

I don't think it jumped time due to the fact that it was normal again that weekend...

I need help! Please.
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Originally Posted by J'sWorld

There is a metal piece on the back of the intake cam that has like 3 tabs. When the cam spins these tabs activate the cam sensor telling the sensor and ecu where the camshaft position is. When the valve cover gaskets are replaced it is very easy bend the tabs with the valve cover when installing the valve cover. I would bet that is the problem.

Originally Posted by Levitas Etan

The valve cover gaskets were changed 10k km with no issues until now.

Could it still be it?

Originally Posted by J'sWorld

Probably not. Possibly variocam actuator. Check fuse 9, 15 in the under-hood fuse compartment. You can check camshaft deviation with appropriate scanner/software and that would tell you definitively about the timing but ultra highly doubt jumped a tooth, almost impossible. Possible cam gear has slipped. Honestly sounds like sabotage but who knows. I would get a second opinion. Not sure where you are located but I can't see engine replacement being cheaper than timing job.

Originally Posted by Levitas Etan

I would love to contact you.
I live in Israel and we don't have any mechanics that can help