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09 CAYENNE TT rough idle after cold start for several minutes

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09 CAYENNE TT rough idle after cold start for several minutes

 
  #16  
Old 06-18-2018, 10:05 AM
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Deilenberger;

This is the exact issue we have been discussing regarding my -11 CTT. (CTT with morning sickness)

Now that the outside temperature is much hotter, the symptoms are "lighter".
Still rough running after starting, and you can still feel it when engine is warm.
But not as bad as when cold starting in the winter.

Gotta be something to do with how the oil pressure controls the VarioCam. One side is probably operating as it should, while the other is OFF.

I also changed both Solenoids without any relief.
My next idea is the actuators themselves. But I will do this at the same time as I pay them to do AH-08!!!

Maxime; Please let me know what they do at the stealership to fix your issue.

Espen
 

Last edited by spirit49; 07-07-2018 at 11:06 PM.
  #17  
Old 06-18-2018, 11:38 AM
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Since we are discussing this issue, I did some searching on other engine brand/types with adjustable cams. The VW W8 is one such engine.

I have been thinking that the Adjusters themselves could be the issue after seeing Deilenbergers explanation. I understand that these adjusters have a fine mesh that can be blocked/restricted by oil crude. A way to "fix" this is to shock the valve/solenoid that regulates oil to the adjusters with up to 12V. Then massage the valve to help clear the crude.

Here is a copy from another forum:
Oh, boy. Last week I was catching up on the German-language W8 Forum, and you all are gonna love this: A forum member there (Reno AKA Blackbird) from Switzerland is a mechanic, and has several W8 drivers for customers. He's done a few repairs according to the factory procedure, and another member has dissected an adjuster housing. When Reno's own car started acting up, he decided he'd try something a little different.

Here's the Cliff Notes version: When your variable camshafts aren't and throw one of the associated codes, disconnect the offending camshaft adjuster solenoid valve pigtail connectors. Briefly "electroshock" the affected solenoid valves several times each with several brief applications of full 12V. Reconnect. Drive. Enjoy.

Yep. A free fix to our biggest common headache. Reno did this to his own car in early November and three customer cars since. One has driven to Greece and back - about 2000 miles. All are running problem-free!

Here's the long version, condensed from two threads. The original is where Reno laid out what he'd done, and the other is the continuing discussion thread started by Markus, who has done further research on the housings and how they work:

1. Background. The W8 uses variable camshaft timing. The intake is infinitely variable over 52 degrees. The exhaust has two positions the cover 22 degrees. To control the positions of the camshafts, the system uses oil pressure, whose flow is regulated by the ECU via the hardware in the camshaft adjuster housing. This hardware consists of two each filter screens, check valves, and magnetic proportional solenoid valves (AKA actuators), one set each for intake and exhaust, per head. Pressurized oil flows from the oil galley in the head/block through the filter screens, through the check valves, and the distribution of oil to either side of the adjusters' piston vanes is controlled by the magnetic solenoid valve position.

The proportional solenoid valves are normally controlled with 0-5V. They consist of a magnetic coil, a return spring, and a piston element - a pretty common control scheme. When no current is applied, the return spring retracts the piston. When current is applied, the resulting magnetic field extends the piston proportional to the amount of voltage. Normally, full extension is achieved with 5 volts.

2. Problem. If for some reason the control solenoid becomes stuck, the camshaft position also ceases to vary according to ECU inputs, which generates all the associated trouble codes and panic at the dealer. There are two possible reasons for stuck actuators: bits of pre-filter screening becoming lodged in the mechanism, or oil sludge gumming up the works.

3. The free fix. (Reno regrets he didn't try to patent what he discovered!) Same for both conditions:

a. Gummed up w/ oil sludge - the piston extends when you apply full voltage (5V). Because it's an electromagnet, applying more voltage only increases the field, which increases the force with which it extends. Markus has done a 12v-to-failure-test, and it took at least 30 seconds of constant 12v on the solenoid before it started to overheat... and it still functioned normally afterwards. Applying several "pulses" of 12V to a stuck solenoid has been shown to break it free, clear the bore, and return it to normal operation. This can easily be done manually with a couple of wires, since the pigtails are easily accessible on the back of each head. On the other hand, one forum member took his broken car to a dealer and asked them to do this, but they wouldn't... at first. They ended up going trying the actuator output test (accessible within VAG-COM), which fully exercises the range of motion using the ECU (so no more than 5V.) It worked, and he had his car back in two hours!

b. Stuck piece of filter screen - the pre-filter screens (AKA membranes) are just that - screens. They are made of ~100um stainless wire, with a mesh size of ~80um. (Your car's oil filter already filters anything bigger than 5um, BTW.) They are apparently the brainchild of an overanxious engineer and serve no purpose besides possibly protecting against first-start damage by factory shavings left in the oil galleys. When camshaft adjuster housings have been removed from our cars, filter screens have been completely eroded away or half gone... on the side of the housing whose solenoid was still working fine! Ergo... small pieces that break off this screen mesh can and do pass through the actuators, and end up in your oil filter. Applying over-volt impulses to the solenoids could also jar loose pistons gummed up by filter screen pieces. Markus from the German forum removed the screens from his new housings since his car was apart for 10 weeks during all this discovery over there (bad dealer story in iteself), and he's also got multiple thousands of trouble-free miles since then.

4. Confirmation & Interesting Tidbits: Reno phoned Hilite (OEM manufacturer of ours and many other variable cam timing setups)... and spoke to their tech line. The voice on the other end admitted that the design for the W8 could have been more robust, but that the method he discovered should work just fine for clearing stuck solenoids, unless the whole unit is complete junk. It is very unlikely that you'll ruin an otherwise good adjuster control housing unless you completely ignore the engine light and rough idle and keep running it hard long after the mechanism becomes gummed up.

Reno also inquired if we'll ever see housings available directly from Hilite (instead of via VW at $$$ prices)... probably not soon.

So... direct from the German W8 community: Do your regular oil changes, but when/if things go south, give your cam adjuster solenoids some electroshock therapy! It's free! The VW-approved solution replaces anything you'd break in the process, so what's to lose?
 
  #18  
Old 06-18-2018, 09:15 PM
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Hello, spirit49

At the point, my porsche dealer cannot figure it out.
Dealer guy tested the almost input values ​to ECU, and the output values. He said all data are normal including waveforms.
He inspected the wiring from ECU to battery and the engine harness, but no problem.

As a possibility, there seems to be some problem inside the engine??
 
  #19  
Old 06-18-2018, 11:08 PM
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As a possibility, there seems to be some problem inside the engine??
They are trying that on me too. I did a boroscope on it, and I cannot find any obvious issues.

There has been several previous issues with Cayenne owners reporting muscle car tendencies (idle vibrations). They have been solved by replacing the solenoids on the backside of the engine.

I did both of mine, and the issue is still there. So the actuators are next, or maybe even the Camshaft adjuster itself.
The adjuster is only a mechanical part, but I believe that this has been the culprit on some engines in the past.

Im wondering if I should just dive in an get all the parts before getting AH08.

New adjusters (650$ a piece). New actuators.

It will add up quickly.
 
  #20  
Old 06-26-2018, 08:09 PM
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https://rennlist.com/forums/attachme..._v6-1-1-1-.pdf


This describes the variocam operation in the 4.8 in entirety.
 
  #21  
Old 12-03-2018, 10:38 AM
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Hello, maxime,

have you solved the problem? I think I have the same issue...
 
 
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