Engine Knock in Spring and Fall

Hello All,

I have a real stumper of a question for the community.  I have a 2013 Porsche Cayenne S that has an engine knocking issue since I got the car.  The real puzzler is that the engine knock only appears under certain conditions.  It only occurs if/when the oil temperature is up 200 - 210F, and the outside temperature is between 40 - 60F.  I spoke to the dealer multiple times and they've dismissed it as "bad/sub-par fuel".  They've recommended I change gas stations which I have done multiple times.  I used to fill up with 93 octane Shell and as per recommendation I've switch to 93 Octane Sunoco but the knock was ever persistent.  I've added a bottle of Techron to perhaps clear some clogged injectors to no avail.  I've read on some Porsche boards that some people had success with a bottle of Octane Booster and I've tried that too again to no avail.  Took it back to the dealer and according to them they hooked it up to the computer and queried the engine computer.  They did detect the knock and told me that its bad gas and recommended that I change gas stations.  Clearly they don't know what's going on or they just don't care; I'm not sure which one.
I'm in New Jersey and it has been under 40F for the past few days and the engine has been sublime and purring like a kitten.  Today it it was in the high 40s low 50s and I heard the knocking again.  Like I said it happens when the oil is up to temperature (200 - 210F) and it mainly occurs when switching from 2nd gear to 3rd gear under low RPMs.  I sounds like pre-detonation because of lack of air in the mixture.  Of course I'm not a mechanic and I'm only guessing at this point.  I'm out of ideas so if anyone could give me hints as to what's going on or know what's going on I would really appreciate it.  Thanks in advance...

While this would be very early for EGR-related problems, I would suggest that you have the EGR valve cleaned. It is very possible that Porsche uses a name other than “EGR” for this component, however…

Apparently this is a known problem with Cayennes. One owner said he had the dealership borescope his engine, but he didn’t say what they found…

http://rennlist.com/forums/porsche-cayenne-forum/779292-knocking-sound-from-engine.html

Apparently older Cayennes were prone to a knocking sound that was caused by pistons scoring the cylinder bores. I don’t know if/when Porsche solved that problem, so your newer model may or may not be prone to that problem. But since you’re out of answers, I’d have the engine borescoped to look for scoring on the cylinder walls.

The knock sensor might be on the fritz. That gadget – your car almost certain sports one – is used to retard the timing when it detects pinging. Knock sensor not working, you’ll get knocks.

Thanks for the prompt reply everybody. I think I might suggest the dealer to take a look at the knock sensor. I googled it and it turns out its a $100 part but its a pain to switch out because of its location within the engine and 1/2 of the cooling system needs to be drained. I will ask them to see if it threw any codes before doing any works.

Jesmed1; thank you for the links. I’ve already seen them but only the first one is relevant to me because that is my current model. The other link was for the previous generation Cayenne and those engines were susceptible to cylinder scoring because of their improper lubrication in colder temperatures. The latest generation of engines have proper lubrication and the inside of the cylinders are coated with some chemical to prevent scoring. But I do appreciate the links since they were an interesting read.

I will stop by and talk to my dealer and give a followup. Thanks again everyone…

Maybe they said they solved the problem, but your symtoms sound exactly the same. Late 90’s v6 Camry’s would starve for oil due to small oil passages. The 05 and up v6 cams starve of oil again, small passages again.