i wish i had insightful mechanical inclination to help - i am merely just regurgitation what i recall reading as a relatively common culprit to this annoying issue.

 

My best guess is that the flywheel gives crankshaft position information to the Crank position sensor. If the flywheel is warped or in some way out of sorts the CPS will get erroneous information and timing of the whole engine will be out. Well mechanical timing would be set by the chains and setup positions of the crank and camshafts but the timing of the spark would be called upon perhaps at the wrong time. I could be very wrong about this.
I can't imagine that an immediate code wouldn't be thrown for such a problem. Again I could be very wrong ...lol
This is possible though as it is an item that would effect all cyls.
On the plus side I am learning a lot about this engine. When it works you have no reason to want to know how the magic happens.

 

fly wheel issue won't throw a code. thats been confirmed by those who fixed their CEL light issue via flywheel replacement - search rennlist for flywheel or DMF, maybe more insight will pop up.

 

Well I can confirm my earlier statement about intake manifold needing to be taken off in order to R and R the resonance tube is wrong. Poking around behind the engine with a mirror I noticed the vacuum line to the resonance actuator was disconnected. I therefore had no choice but to remove the tube and was able to do so with some major contortions. You can reattach the vacuum lines with the tube in place but you have to know how everything sits back there behind the tube first which is hard to know if you haven't seen it.....has to be done by feel as there is no sight line. Those rubber unions checked out good so all back together with vacuum attached. I'm going to rule this out as being an existing issue as the nipple on the actuator was clean unlike everything else in the engine compartment. Must have just knocked it loose doing some blind cleaning with a rag. Glad I caught it before I started putting everything back together. There are several things on top of the engine that would make good use of lowering it in its mounts. This is ok up to a 30-40 mm max via the engine mounts. Injectors would be a good candidate for this procedure and is pretty simple with these engines (lowering that is).

I'll look into the flywheel theory. Going to get everything else 100% first because the flywheel is likely a dealer visit.

 

Pulled all 4 cam actuators (everything still installed..so it can be done as easy as plugs with the required extensions and palm tools) and all actuate. Not sure "how they are supposed to actuate"....but with 12v connected in either polarity they move...so I might call that good. Not sure if that is a good diagnosis. Any info would be appreciated. I do note that my actuators are the original from 2005 and they have been superseded by one part number for that year. I know these have been a failure point so just wondering what the issue was and what problem the new dash number fixed,
I also see that there is another part number for the lift control actuator in particular that looks different and has a different part number. It is just slightly ahead in the engine number production range. Wonder what that change was and if it can be used on earlier engines.

Should I roll the dice and buy 4 new actuators for @900.00? They seem to work manually and I have never had any camshaft actuator codes. However they are a common cause of misfire and have been superseded by a new part.

 

Problem solved. Unfortunately I don't know for sure what the problem was as I replaced a few parts at the same time. Those parts included new starter/alternator harness, Plenum rubbers, Valve lift solenoids, and coils/plugs. I had the misfires after the coils/plugs so I don't suspect they were a major factor. I have a feeling that the valve lift actuators were the ticket. B+ harness that I removed was the improved version and had been replaced a few years back (and looks like new) so I'm not suspecting I needed to do the harness. I also bought a smoke machine just to rule out any intake or AOS leaks.
Anyway, now not a single misfire according to Durametric. Only issue I have at the moment is a higher camshaft deviation on bank 2 than bank 1. I'm just going to drive it for a while and do some logging. Perhaps I'll go ahead and replace the cam timing solenoids later if the deviations don't even out.
Big thanks to all that helped out with advice.

 

so basically valve lift solenoids?

 

Yes that is my best guess. I maybe had a small intake vac leak at the plenum with the crack in the rubber sleeve but it was running so rough that I suspect that could not have been the major issue. The valve lift solenoids bench tested fine and didn't produce codes because they hadn't failed completely but just weren't functioning as the precise hydraulic valve that they are. So yes I did toss a few parts at the issue that were not required such as plugs/coils, vbelt, alt/starter harness, but those are good things to get done anyway and she's running better that ever. With the symptoms I was having I would never have gone straight for the solenoids. Unfortunately Durametric does not give actual values for valve lift as far as I can see. You can actuate the variocam plus which just produces a sound if they haven't completely failed, but no numbers to indicate their proper function. These valve lift solenoids have been superseded a few times over the years, sometimes a good indicator that issues are common.

 

when you stated it was running rough, do you mean at idle per say at stop lights and intersections? noticeable vibrations (nothing MAJOR - but enough to notice)

 

Never got that far in the process....as soon as it came off high idle it would missfire in all cyls and have to be shut down as the rpm would stumble around 500. Vibrations extremely noticeable to say the least. My understanding was that at high idle on initial cold start the valve lift is adjusted to it's high limit. Only problem was that after it switched to regular idle the valve lift failed to adjust to the lower lift making the mixture and timing incapable of sustained idle, with multiple misfires. To mess around and allow it to shake and such would not be my recommendation.

 

This issue has come up again a couple times recently on the Facebook 997 page. I thought I would bump it up just so that it gets fresh again. Maybe they are getting to be that age where Variocam solenoids are going to be failing. Easy and relatively cheap DIY.

 

I rarely waste the space by using the quote reply, but I read all your trials and tribulations back in the day and know how frustrated you must have been.
My inclination if you had posted this problem today, would now be to tell you to take the car to a tech who knows how to use a scope. A good diagnostician who has the documentation for the vehical should have been able to narrow down the problem within an hour. More than a code reader, a scope will document multiple timed events on a crank angle timeline. If a cam is not in the right position given a certain operating condition, the tech can see that, if the crankshaft fails to accelerate at a certain point, the tech can tell what cylinder is the issue. Once a tech finds the exact problem, then the solution is just a logical process of elimination. The whole problem for the average owner is finding a tech who actually knows how to use a scope, and not paying 1, 2 or 3 garages who claim they do.