deilenberger

The CTT (all the 4.8 turbos, 958's included..) use the single-prong NGK. It's specific to this engine, and I can't find any real crossover to another reputable plug (like Bosch) for these engines. PITA since the plugs are rated for 30,000-mile change interval and run at least $10/each.

Brainz

Hmmm. Perhaps that explains kadn33's issue: those 4 prong gaps look huge relative to the [. 032"] that I think was spec'd for the 06 CTT.

kadn33

They are supposed to come pre-gaped from factory. I'll compare old vs new gaping when I do the job but I am expecting it to be the same for all.
And to be fair I have to say that my issue might be well related to other components I noticed such a ticking fuel purge valve or a leaking crankcase vent hose with a temporary repair currently. I might have a bad left fuel pump as well causing the rough idle and occasional engine stall when I drive from flat to a downward slope in idle. And of course the coils are always there even being the last revision and having no cracks.
I'll start with the plugs and will dig in further if that doesn't fix it.

deilenberger

The 4-prong plugs can't be "gapped" - they are as they are, and that's how they come from the factory. You would need a needle-gauge to measure the gaps, and then how do you adjust it? FWIW - I have never seen instructions to set the gap on 4-prong plugs. And I'd expect the old to have much larger gaps and the center electrode to be squared off somewhat.

Brainz

Agree, no gap adjustment on the 4 prongs. I was thinking of it more from the standpoint of whether the 4 prong plugs could be more likely to cause misfires than the narrower-gapped single prong plugs. I don't actually know, but I'd not run a 4 prong if it was not spec'd.

kadn33

I completely agree. But in the context of how things are done here and the standard of the shops being "do it quick no matter what" I am just suspicious of any work done previously. I had to re-do a couple of crapy repairs I found in the car already. So comparing plugs is more about fulfilling my curiosity or call it confirming my suspiciousness, but the new ones will go in right as they come out of the box definately.

For the Cayenne S, 2004 in my case, the 4 prong ones are the correct so no issues there. Actually one shop tried to sell me a 4 prong plug but part number FGR7KQE0 swearing it was 100% compatible "same same" as they say here but I refused to get the OEM FGR6KQE shipped from USA instead. You really have to be 100% sure of what you get and where you get it from, here.

Colly

I had a separate post on this just a few days ago. I think it probably is the coils and going to find out soon when I get it in for a proper service. However I just wanted to check with you guys. Mine does stutter even so slightly initially on acceleration, but not constantly. However it seems to 'judder' when sitting in traffic. Kind of skips a beat and wobbles. Even my wife noticed it. Would this be the coils or does it sound like something else?

Brainz

Sounds like you have both a stutter and and a stumble. Here's my descriptions of some common Cayenne maladies and their driving sensation based on my experience (and having fixed each):

Stutter: Usually happens at mid-to full throttle. Feels like a quick pulsing of power rather than a smooth push. Most noticeable in 2nd and 3rd gear under acceleration in the 3000 - 5000 rpm range. It's a "high frequency" stutter, where the pulses feel quickly on/off and of equal magnitude -- like you're engine's losing about 12.5% of it's power quickly and repeatedly (because it is). This, IMO, is the epitome of a failing coil. Your passengers may not even notice.

Stumble: Instead of a smooth, consistent idle -- you get rough, irregular idle which "skips a beat or two (or more)," shakes/vibrates the car a bit, and, if bad enough, may feel like the engine is going to die. Unfortunately, this could be lots of things: coils, vacuum leak, MAF, O2s. Passengers might notice this if it's bad enough: "your car going to make it?"

"Hopping" Judder: This is more of a transmission feeling and tends to happen somewhere between 1500 and 2500 rpm under moderate acceleration, typically under 50mph. It's a "hopping" drivetrain sensation, and is lower frequency, and higher amplitude than a stutter and may shake the car a bit. My personal view is that judder can be caused vacuum leaks, wrong transmission fluid, valve body, and transmission controller calibration. Vacuum leaks are the most insidious, because it feels like your transmission is slipping -- and, in fact, it may actually be coming from your transmission, as instructed by the transmission control module, which is responding erroneously to a vacuum leak. I think the judder is an issue with the lockup of the torque converter. You can usually "drive around" it by keeping rpms above 2500.

Washboard Judder: This feels exactly like riding on a washboard road and happens around 2000-2500 rpm usually under very light acceleration or coasting, typically under 50 mph. It's a buzzy, high frequency feeling that oddly comes through the steering wheel. In my experience, it was tracked down to a leaking EVAP purge valve. Like the judder above, I believe it's due to a vacuum leak of a certain type confusing the transmission controller and causing a high frequency pulse in the torque converter lockup. It often only occurs early in the first drive in the day and goes away thereafter as engine conditions change.

Bang: Typically on a 5/4 downshift. It's a hard jerk through the whole chassis, that some describe as like being hit from behind. Everyone in the vehicle will notice this. It's the valve body.

Slip- Grab/Bang: This happens if your transmission is underfilled. It happens in two ways: 1) You'll usually notice it backing out of your driveway first. After reversing, you shift to Drive for a second or two you get nothing and then it grabs and jumps forward. After that it mostly seems OK for the rest of your drive. 2) If your trans is underfilled and you drive up a long incline (like an overpass), it may end up starved of fluid which will depressurize and repressurize some of the clutches in the trans causing a nasty slip/bang -- like "popping the clutch" at speed. Everyone in your car will assume you just got rear ended. It's pretty violent. NOTE: if your trans is really underfilled you just wont get any drive at all -- this usually happens right after it's been serviced.

Karl -- The Cayenne Gnome: Karl has a hammer and lives under the center console in your Cayenne. When your driveshaft center bearing is going out, Karl starts by gently tapping under your center console with his hammer when your accelerate -- Left hand drivers will feel it under their right elbow. If you ignore him, and/or accelerate more feverishly, Karl really starts hammering -- the faster you go and more aggressively your accelerate, the more Karl hammers. He will not be ignored. I recently appeased Karl with a Jimi fix, but interestingly, it took a few drives to him to be convinced that the Jimi fix was acceptable. He still tapped a bit a bit a first, but eventually the hoses and zip ties must have settled in, as Karl no longer reminds me he's there.

kadn33

As a follow-up on what I reported here's the status now:

I replaced the spark plugs yesterday and spent many time checking components around. First thing I noticed was no more oil accumulation in the plugs 5 and 6 but only drove a few hundred miles after my first check: plugs 7 and 8 were still dry. Bank 1 however was quite the opposite and all the plug well threads were rusty and had to spend a considerable amount of time cleaning both banks. Worth it anyway because the new plugs went in really smooth.
While I was there I wrapped the crankcase vent lines completely with tape because a few tiny cracks were developing and I hope they hold until I get new parts or a proper repair solution and found the AOS diaphragm slightly cracked: a new one is on the way already.
The engine support arm was not cracked but the middle rubber was slightly deformed towards the engine. Not sure if this adds to the vibrations.
Everything else fuel / intake / vacuum related seems to be fine, including the coils.
So right after finished I did a throttle body reset and went for a short drive: The misfire I was noticing is gone and the car has become smoother in the 0 to 2000 rpm where there used to be some stuttering and in overall the car runs smoother - even gear changes, specially reductions are better - and has recovered some power in lower rpms plus seems to be slightly quieter. The vibration coming to a stop is better now although the engine mounts need replacement. In my opinion the plugs 5 and 6 were misfiring or not firing adequately and affecting the riding comfort directly. I swapped their coils with plugs 7 and 8 and will check in 1000 miles or so.
However I can still feel the idle is not 'round and steady'. Maybe the AOS and new vent lines help or its just the engine + trans mounts.

Next steps are:
-I will log O2 sensors and Fuel Purge Valve values in VCDS to see if there is something wrong there although I believe there should be a CEL for these.
-Check the plugs condition in 1000 miles.
-New AOS diaphragm
-crankcase vent lines repair/replacement

If after the above the idle remains the same, then I'll leave it there for a long while.
In any case any input is welcome.

Regards.