Our new to us CTT seems to be a bit grumpy in the morning.

Whenever the car is cold, or have been sitting for a while, it has a pretty moderate vibrations just after being started.
The engine goes in to the higher idle, and there is almost like there is a misfire going on. By giving it a little xtra rev, the vibrations normally disappear, and the engine idle returns to normal values.

I just received my IcarSoft POR II, and the only Fault Code that I can see connected to this issue is DME P1364 "Valve lift control cylinder 5".

I deleted the fault so to see if it comes back.
Im on the road now for work, but keen on using the spare hotel time to try to figure out what could be the issue.

My initial thoughts is that the vibrations was due to a bad spark plug or coil, but I cannot see that this should only be visible for a short time while the engine is cold.
However, the spark plug has never been exchanges since the car was new(according to the service log book). 84000km(51,5'miles)


I cannot find much info on Fault code DME P13XX on the 958, but it seems that a lot of other Porsche types have had issues with Valve Solenoids.
But that figuring out how that system works is above my pay grade.

Worth mentioning is that the engine has the bad VarioCam bolts installed. Hopefully these aren't involved, as there is no recall for AH08 in Europe at this time.

 

Your plugs are WAY overdue. Change interval is 30,000 miles for the CTT. As far as the VarioCam bolts recall - the way it "happened" here was a response to a lot of reports to our regulatory agency (NHTSA) about failures and the danger involved if they do fail. Plus sending them info on prior recalls Porsche-AG issued in other countries for the same issue.

That might be something the euro Cayenne V8 owners might think about coordinating. I'm sure you have something similar to the NHTSA in Europe - find out how to report things like this and do it.

 

I guess we can start out with new plugs(and maybe new coils, at least on nr 5), to see if the problem persists.
But do you really feel that plugs would have an issue only at the initial start up of a cold engine?
My feeling is that the Cam adjuster is struggling on one bank on initial start up, but not the other. Therefore the moderate vibrations. but then again, I guess a full row of fault codes should be visible on that side.

I will be working on the AH08 recall issue the next couple of weeks with Porsche Switzerland, then see what comes out of it. Will report progress in the appropriate thread.

 

Refreshing this thread as I now have gone through several troubleshooting steps since the last post:

+ All plugs changed
+ All coils changed
+ Changed Variocam solenoid on bank 5-8

There is no change whatsoever. Vibrations are still there on start up from cold engine.
And I can still feel that the engine is somehow vibrating, missing even after it is warm.

Took it to the local Porsche dealer today, and spent an hour with the shop manager.
Really nice guy, that listened as I went through all my motions and previous troubleshooting points.
Since the engine was warm, he couldn't read the live stream as would be when cold, but he did recognise that there is a non-normal vibrations present.
Plan is to leave the car overnight and see of the livestream can point us in the right direction. Car hasn't thrown any error messages since I deleted the P1364 "Valve lift control cylinder 5".

We were brainstorming for about 20 minutes what could cause this.
I personally are leaning towards the fact that sensors(solenoids or the actuators) in the vario-cam system are at fault or has some sludge in them. Thats the only way I can explain why the vibrations are stronger when the car is cold.

The shop manager is leading towards a fuel issue.

This CTT is using a lot of oil. We keep topping it off.
Reading posts on this issue form other CTT's, it might be that this car never had the Oil-air separator replaced.
At 59000miles/95.000km, it can be that all this oil has been passed by into the intake and has been building up on the intake valves.

The shop manager thinks that I might have glanced/damaged cylinders and that the oil is passed through piston and the walls. If that is the case, Im fu......

I have a proper borescope, and will try to make video/pictures of all the cylinders and valves through the spark plug holes tomorrow.


So unless tomorrows video sessions shows any major deep engine issues, my next troubleshooting steps are as follows:

+ Change Cam solenoid on bank 1-4
+ Remove valve covers to get to the Cam actuators
+ Look into fuel pump issues.

Any help appreciated.

 

Before disassembly of the engine - I'd suggest checking the drivers side intercooler plumbing. That's the side that gets an oil buildup of the air-oil separator hasn't been updated. Usually it's evident even without opening the plumbing - there will be oil around the joints in the plumbing.

If so - I'd certainly look into replacing the AOS. Mine ate oil (according to the service records for the first owner that I got) until they performed the "Campaign" to replace the AOS. It now is capable of going from coast-to-coast across the US (about 8,000 miles) and not needing a quart of oil.

If there is a lot of carbon buildup on the back of the intake valves on one bank of cylinders due to the AOS - that could easily account for the bad running conditions.

Removal of the air-intake would be required to check it out, but that's easier than doing what you intend to - and actually to do what you intend to - it's much easier done if the air-intake/plenum was removed.

 

If this is the case, why would the vibrations be higher when the engine is cold, then get quickly better after increasing rpm slightly.

Bad valve seating should be a constant issue I would think.

For the borescope inspection.
How can I turn the cams without having to run the starter?

 

The problem isn't bad valve seating. The problem is absorption of fuel by the carbon built up on the valve. When the engine is cold - the injection system purposely pumps a rich mixture to help the engine fire off quickly. If you have heavy carbon buildup - the carbon absorbs the rich mixture, leaving a normal or lean mixture that's hard to fire off cold. Then when it does fire off finally - the carbon heats up releasing the excess fuel into the stream of air flowing past the valve - resulting in an unwanted rich mixture = Lumpy idle.

Increasing the engine speed makes the fuel evaporation out of the valve happen more quickly until the system can finally bring the mixture under control.
Why would you be worried about the cams? A borescope doesn't go through the valves - it goes through the spark plug hole. And you turn the engine over by removing all the plugs and using a big wrench on the crankshaft bolt at the front of the engine.

 

I need to borescope the cylinder walls to rule out the oil usage theory the shop manager has. I did so today, and I did encounter a couple of pistons close to TDC.
However to get to Crankshaft bolt will require some extra work.

The walls of the cylinders I could access looked ok to my eyes
I would expect some heavy scorching to claim that the oil gets pushed through between the piston and cylinder walls. Im tilting to the oil separator for oil usage.
It is the -21 version. The latest separator is -22. Malfunction could be an issue.

 

Had a look at the intake ports as well today.

Bank 1-4 was much more oily than the 5-6.
Both sides had carbon build up, but not too bad.
The build up was soft, and I could remove it by carefully using a pick and then cleaning the port and valves with a brush and brake cleaner.

The pictures is before cleaning.
I dont think it would be the reason for the rough idle and vibrations.



From row 5-8. Not so oily as the opposite side.





More deposits and a more oily look on row 1-4

 

5-8 don't look bad at all, 1-4 need cleaning. The difference in flow between the two banks may make a difference in the idle quality.

BTW - the photos of the piston crowns and cylinder walls... the top one looks like the carbon on top of the piston is wet and crumbling. The top photo looks different - a rather large buildup of carbon, but uniform and solid and dry. Which cylinder was the wet one? And is it only one?

Things that come to mind for a wet cylinder are:
- Leaking injector on a cylinder
- Bad ignition on a cylinder

 

Here are some video of the cylinders I could access the last days.

 

How do you get in there and clean those? Amazing footage. The Camila Cabello ‘Havana’ was a nice background music bed as well lol.

 

Yeah, the computer records background noise too

The borescope goes through the spark plug hole.
The 2 innermost cylinders(to the firewall) Im unable to check as the scope is of a rigid type.

The intakes can easily be cleaned by removing the intake manifold.
The carbon build up is of the soft type. I can only clean the top of the valve stem with a brush. A walnut blasting would be the best way of doing this, but I dont have the equipment.

 

Curious what sort of boroscope you're using.

There does seem to be some variability between the cylinders - some appearing wet (perhaps the injector just sprayed? I assume you're using the starter to rotate the engine?) some having more carbon buildup than others. The one does have what appears to be a gouge in it - but it certainly isn't big enough to be concerned about, and if I had to guess - it may be a very shallow scratch caused by some carbon.

Do you have a compression tester? That might show something of interest if there is anything to show..

 

I use the ablescope.

There is a non rigid version too. That would probably work better on car engines.

I didn't bother about turning the engine over to do the cylinders at TDC.
The results I got tells me that the oil isn't disappearing through the cylinders.
I will order a new oil separator to see if that solves it.


Managed to replace the Cam solenoid on the right side now. That wasnt too easy, as it is so little space between the firewall and the engine. Just getting the vacuum pump out is a big job.
Anyway, the result is the same. Still the rough idle.

So the search continues.
Shop manager is leaning towards the fuel system. He will need the engine cold to read the live stream on hos diagnostic system. I believe he can see more than me

I think we can rule the ignition system out.
Variocam too. Next would be the cam actuators