09 cayenne TT
108000km

Hello,
The idling is unstable for 4-5 minutes after a cold start but NO CEL and no error with DURAMETRIC.
Checking some actual values, I found that both intake camshaft angle is more advanced than the setpoint.
After start 4 or 5minites, intake camshaft angle become the same angle as the set point, and the idling becomes stable.
Once becoms stable, trouble doesn't occur until next cold start.

I have checked both cam adjuster solenoids and oil pump solenoid, smoot movement, no sludge.
And have replaced chain tensioner.

Here is pictures of Durametric screen after cold start.

Does anyone have similar problems?

At the same time, I am worrying about whether the oil pressure value is right or not,
and is it correct oil pressure setpoint shows 0.0?

 

Do you have an oil pressure display on the dash? What's it telling you? The 2.6 Bar showing actual oil pressure is just fine..

I'd suggest plotting the output of the pre-cat O2 sensors. Lets make sure both are working correctly..

 

I had a rough idle right at start a couple of years ago, what fixed it for me was new plugs/coils.

 

Thanks for writing, deilenberger.
Mine has no oil pressure gauge on dash, or I might just don't know?
So I checked actual value through durametric.
Both pre-cat O2 sensor voltage is about 1.9 - 2.2V while rough idle.
Does O2 sensor work correctly?

 

Thanks for writing richie996

I replaced plugs 1 year ago, but coils.
Misfire is not found through durametric.
I will replace new coils, just in case.

 

I've replaced coils for new ones.
But no change.

Should I change cam adjuster solenoids?
I checked the movement at 3V,
but cannot judge whether they are functioning perfectly.
Does anyone have experienced cam solenoid failure?

 

 

Durametric does offer the capability of looking at the camshaft angles - the expected angle and the actual angle (ie - how the Variocam is working).. that would be worth doing. See if the camshaft is doing what the ECU expects it to do.

 

 

DUnno, what are the expected (setpoint) angles?

 

Thanks for repley

While the warm up phase, setpoint is 120 CA and actual angles are 100 CA.
Then disconect solenoids, both setpoint and actual angles going to 130.8 CA.1 or 2 minutes after engine start, idling become stable, setpoint and actual angles are 130.8 CA.
But actual angles going advancing about 30 CA compared to set point by blipping.

After another 4 or 5 minutes, the symptoms also improve.

 

SO the symptom is - the cams aren't where they're supposed to be during the warm up phase.

Lets see if I understand this correctly:

1. Warm up phase - solenoids connected - the ECU is calling for 120 degrees and the actual angle is 100 degrees advance?

2. Warm up phase - solenoids disconnected - ECU calls for 130 degrees and the cams are at 130 degrees?

3. Warm up phase - 1 to 2 minutes into it - the ECU calls for 130.8 degrees and the cams are at 130.8 degrees? This is with the solenoids connected?

#1 scenario - car idles crappy
#2 scenario - car idles OK
#3 scenario - car idles OK

4. Engine warmed up - solenoids connected - throttle blip = cams advance 30 degrees past where the ECU is calling for?

One thing rattling around in my mind - I recall sometime long ago - someone having this sort of problem, and the issue turned out to be some sort of in-line filter with the solenoid. I think it was on the feed to it, but it could have been in the output. I vaguely recall the filter being in the block, but accessible when the solenoid was removed.

What you've described above if I understand it correctly sounds like the cam adjustment is slow. When the engine is cold it doesn't advance enough (#1). When the engine is warm it doesn't return to where it should be quick enough (#4).

It sounds as if the ECU is sending the correct signals but the system isn't responding as it should. That means a problem in the oil circuit.

It's not clear to me if the Variocam normally keeps the cam advanced and the control of it is to retard the advance, or if the cam starts out retarded and the Variocam advances it. I'll have to dig into it a bit and see if I can determine this.

You've replaced the solenoids - and apparently both banks are doing the same thing?

That to me sounds like a hydraulic problem, perhaps with oil pressure. What weight oil are you using?

Shame this discussion wasn't taking place on the other forum (Rennlist) since there are a few Porsche techs who sometimes will comment on oddball issues like this one..

Off to look for an operations description of the Variocam system...

 

Hello deilenberger

Thank you for arranging problems and sorry for my poor English.

I was thinking the same thing.
Main cause is that slow oil provision to retard chamber of camadjuster.

First, I tried 2 different viscosity of oil.
One is 0w-40, the other is 5W-50.
But symptoms did not change.

Next, chaging both solenoids, but a problem wasn't settled.

 

There is also a check valve for the circuit going up to the Variocam solenoid that is supposed to keep oil in the circuit on engine shutdown, so the Variocam can react quickly on cold startup.

I also looked at how the Variocam adjusters work - and it's a double circuit device, oil pressure in one circuit moves it in one direction, and oil pressure in the other circuit moves it in the other direction.

The fact that yours apparently isn't responsive to the settings asked for by the ECU during cold startup would make me think there may not be enough oil pressure on a cold startup, perhaps due to a defective check valve. I'm not sure where the check valve is located - it may well be buried inside the crankcase or be part of the oil pump. I'll look at my service manual and see if there are any answers to that.

Meanwhile - info from a technical introduction to the 955 series Cayenne - all about the Variocam system:


















To me - this documentation points to several possible causes for slow actuation on startup:

1. The check valve may not be working correctly, allowing oil to bleed down
2. The locking pin may not disengage quickly after the engine is started and oil pressure is present at the Variocam adjuster.
3. Low oil pressure at the solenoid valve due to clogging of the feed line. I believe there is a mesh filter ahead of the solenoid valve. It (from memory of a discussion about it) may be located in the block and accessible by removing the solenoid valve.

And I suppose there is also the possibility that the adjusters themselves have worn seals allowing the oil in them to bleed out when the engine is off for some time - and it takes a bit of time for the oil under pressure to refill them and make them active.

This is where it would be great to have a Porsche tech step in and give his thoughts..

 

Thank you deilenberger

About check valve
I also have read p002cayenne.pdf from web site.
I can't find check valve on the parts list and I also think that check valve may cause this problem.
If check valve was remain opend, the cylinder heads have insufficient hydraulic pressure,
then I will hear the tappet noise immediately after engine start?

About lock pin
Is it released by supplying a little hydraulic pressure from advanced oil line?
if lock pin can't released quickly, camshaft angle is maximum retard.
if broken and can't lock, I will hear distinctive noise 1 to 2 seconds after engine start....

The day after tomorrow, I will take my car to the dealer.