New member with 996 camshaft issue

pauldowney996 · 05-29-2015, 06:30 AM

Hello to you all. I have been browsing your fantastic forum for years, and it has given me loads of helpful information. So thank you.
Now here is my first post.
I have a 2002 996 3.6 which has a bad misfire and a diagnostic code of P0344.
I started by changing the bank 1-3 camshaft sensor. No change. The next theory is the actual camshaft has to be changed. So the engine is now half stripped with all 4 cams accessible. I now have a disagreement with the mechanic. I believe that with the engine at TDC all 4 cams should have the slots at the ends vertical. Can someone please confirm this. Because on mine 3 are vertical but the intake cam for 1-3 is of by about 5-10 degrees.
This is the same cam giving the error.
Can anybody advice whether the cam could somehow be out of alignment, maybe due to the tensioners or the variocam.
Any information would be appreciated.
Thanks
Paul

BYprodriver · BYprodriver's Garage

With engine locked at TDC all cams should look similar with the groove between the simi-circles parallel to the cam cover mounting surface. If a cam is not in that position it needs to be retimed

pauldowney996 · 05-29-2015, 06:50 AM

Quote:

Originally Posted by BYprodriver

With engine locked at TDC all cams should look similar with the groove between the simi-circles parallel to the cam cover mounting surface. If a cam is not in that position it needs to be retimed

Okay, so how can 1 cam get out of time?

BYprodriver · BYprodriver's Garage

Quote:

Originally Posted by pauldowney996

Okay, so how can 1 cam get out of time?

Something caused the timing chain to jump teeth on the timing gear, IMS gear slipped on the shaft,etc. You have to dig deeper til you find the problem. I doubt it's the camshaft.

JFP in PA · 05-29-2015, 07:14 AM

Long before I would be taking it apart to check the cam allocations, I would run a cam deviation value check with a Porsche specific diagnostic system to see where the cams really are.

pauldowney996 · 05-29-2015, 08:38 AM

We couldn't do the cam check because of the P0344 error code.
If it is caused by the sprocket on the IMS wouldn't both cams on th 1-3 bank be out of time. The exhaust camake is correct.
Can the Sprocket on the inlet camshaft slip?

JFP in PA · 05-29-2015, 11:47 AM

Quote:

Originally Posted by pauldowney996

We couldn't do the cam check because of the P0344 error code.
If it is caused by the sprocket on the IMS wouldn't both cams on th 1-3 bank be out of time. The exhaust camake is correct.
Can the Sprocket on the inlet camshaft slip?

Either can lose allocation by having he chain slip or a problem with the VarioCam unit. At TDC, you cams should look like this:

pauldowney996 · 05-29-2015, 12:22 PM

So I can try to see if the chain has slipped, but how does the variocam mechanism work?

JFP in PA · 05-29-2015, 01:26 PM

Quote:

Originally Posted by pauldowney996

So I can try to see if the chain has slipped, but how does the variocam mechanism work?

It is a hydraulically operated device that alters the cam timing to increase power. Do a search, Porsche has published a lot of drawings and info on both the VarioCam and VarioCam + systems.

pauldowney996 · 05-29-2015, 01:31 PM

Okay, sorry that was not an appropriate question, I have found my answer from Google.
That goes back to my original point of the dispute with the mechanic. He says that the cam is out of time because of the P0344 error, and this error came from the fact that the segmented disc at the end of the intake camshaft has moved and not sending the correct message through the sensor. Thus a new camshaft is needed.

pauldowney996 · 05-29-2015, 01:32 PM

Has anyone had experience of the disc on the camshaft moving? The Porsche main dealer mechanic says he has. ....

JFP in PA · 03:19 PM

The VarioCam system on the 3.6L is adjustable with slots in the drive system that allow you to reset the timing if needed, the cam does not need to be replaced to do this. If you have access to the 996 Bentley manual, start on page 15-52 which shows how the system goes together and adjusts using tool 9685.

I'm not sure why the mechanic thinks it need a new cam as the entire VarioCam system can be unbolted from the cam itself.....

pauldowney996 · 05-29-2015, 11:32 PM

Okay, but what is the cause of the P0344 error?

JFP in PA · 05-30-2015, 06:34 AM

Quote:

Originally Posted by pauldowney996

Okay, but what is the cause of the P0344 error?

Usually a bad cam position sensor, but as you said one of your cams are not in the correct position, the cam may be out of allocation (timing). If one cam is out, resetting the allocation (the VarioCam unit is adjustable with the correct tools) should fix it, assuming the sensor is still good. If that does not correct it, replace the sensor.

pauldowney996 · 05-30-2015, 08:50 AM

So there is the root of my problem. I think that the timing just needs resetting, but the mechanic says that won't help because of the disc on the camshaft that activates the sensor in misaligned.
The actual sensor was replaced before and made no difference.

JFP in PA · 05-30-2015, 02:46 PM

A couple of things are bothering me here; you noted that at TDC the cams did not all line up correctly, which leads me to believe that the cam allocation is off. Yet your guy claims that the "shutter" disc has also moved (something I have read about but personally have never encountered). As I have not seen one of these with the shutter disc moved, I don't know how you can tell it has moved (it is press fit onto one cam). Perhaps that would be a good question to ask him.

If the car was in my shop, with the problems noted above, I would reallocate the cams in question to set a known baseline, and then clear the code and see if the cam allocations make sense. If they do not, or cannot be read, and the code reappears, then the shutter disc may be your culprit after all, which would require a cam swap as I know of no procedure to reset the shutter disc, other than to replace the cam shaft itself.

pauldowney996 · 06-01-2015, 04:33 AM

So, firstly thanks for your information so far, now the mechanic has suggested that maybe the problem is with the camshaft adjuster (the variocam sprocket) at the end of the intake cam. Have you had any experience of this failing?

JFP in PA · 06-01-2015, 08:20 AM

Quote:

Originally Posted by pauldowney996

So, firstly thanks for your information so far, now the mechanic has suggested that maybe the problem is with the camshaft adjuster (the variocam sprocket) at the end of the intake cam. Have you had any experience of this failing?

Yes, the VarioCam units can and do fail. Fortunately, the entire system can both be replaced as well as adjusted without replacing the cams.

pauldowney996 · 06-01-2015, 01:16 PM

So after some more research, it looks like you have solved my issue. Thank you very much. The next question is, if I have a rattling tappet, do I need to replace all of them, or can I identify which is ones are defect. They seem to be very expensive, especially the inlet ones.

JFP in PA · 06-01-2015, 01:37 PM

Quote:

Originally Posted by pauldowney996

So after some more research, it looks like you have solved my issue. Thank you very much. The next question is, if I have a rattling tappet, do I need to replace all of them, or can I identify which is ones are defect. They seem to be very expensive, especially the inlet ones.

Cam followers for the VarioCam + are pricey. If the individual culprit can be identified, you just change that one. Just also be aware that a lot of sounds typically attributed to the lifters can actually coming from something else (loose tensioners, etc.), so before spending the time and money, make sure you are positive it needs replacing.