996 Turbo - Cam Deviations of -12.5 and - 15 after rebuild...

Had my engine rebuilt about 4 years ago. Only just had the time to put it back in and I've got deviation of -12.5 on Bank 1 and -15 on Bank 2. I can't see that my old version of Durametric will do solenoid activations but happy to be told otherwise. Where do I start? It's both cams, and they seem rock solid at those numbers. Actual Angle at idle for both is around zero for both. This will increase to +30 when the throttle is blipped, but if I steadily raise the revs, they stay around -2 deg. The only other issue is a miss fire on cylinder 3, but not that bad. I want to explore all options before getting the dropping engine stage. Could the position of the crankshaft sensor be a potential? is so, what way should I try and adjust it? In or out? Any help will be much appreciated.

anyone with a durametric, a 996t, and ten minutes.... - 6SpeedOnline - Porsche Forum and Luxury Car Resource 996 Turbo / GT2 - anyone with a durametric, a 996t, and ten minutes.... - Just looking to see if someone here has ten minutes to spare at some point and hook up their durametric cable to their car and log/check a couple variables under the DME. I'm looking to have you log: RPM Cam position 1... www.6speedonline.com Possibly some useful info in this thread If you google 996 turbo cam deviation quite a few results come up

Yeah, I’ve googled it to death, and found that one, as I’m clutching at straws, hoping there might be something else worth checking before I bite the bullet and take the bloody engine out again!

Yours seems very similar to the thread I linked to, except yours are more negative! You can't adjust the timing with the crank sensor! Is it just the deviation codes you have? As much as you don't want it to be set wrong I think that's the direction your headed unfortunately Mac

It does. As I said, I'm clutching at straws. Well, I guess I won't be taking it to Le Mans Classic next week!

If they are reading zero at idle and advancing as normal - where is the deviation occuring?

I don’t know the Mezger in that depth at this stage but thinking more broadly I would be looking at the commanded variation assuming it has variocam on both intake and exhaust although I suspect due to the age it’s only on exhaust.

Hmm thinking some more… and trying to think practically.. I would set cylinder 1 to TDC with a dial bore gauge then stick a leak down tester on it and see if the valves are open. If you get high leak down the timing is probably out. If that is 15 degrees out that will be absolutely pouring out of the intake and exhaust and potentially is also your misfire.

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Yes this Sim I would definitely check the commanded variation first. Which is basically what the ecu is trying to accomplish with the variocam. The timing will be adjusted to get the best mix of fuel efficiency and power. Don’t see how the timing can be perfect at idle then run out unless the hydraulic tensioner is failing.

My understanding (and happy to be corrected) is that the Cam deviation numbers are the number of degrees difference between the Camshaft in relation to the Crankshaft. The actual values are the actual camshaft ignition timing which is why they change with the variocam, which I believe is on the intake only. I swapped the coil pack from cylinder 3, which has the missfire, with cylinder 1 (all new coil packs) and missfire still on 3, so I'm leaning towards this being a result of the timing being out as well. Chap who rebuilt the engine is thinking the cams may not have been set correctly now as well. I just wanted to make sure I'd checked all other possibilities before pulling the engine. This vide shows the readings. Interestingly, the actuals only go up to 30 degs when blipping the throttle, and not when the revs increase steadily.

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Yes so that deviation at -15 might not actually give you the full picture it might actually be futher than that but that is potentially the max that is displayed. If you have an oscilloscope you can map the cam and crank position to find out the exactly how far it is out but I suspect at this point it’s looking like you might have to pull the engine to check. The engine turn over a few times ok prior to starting? Suspect it did so the valves should be ok.

Yes the "camshaft deviation" figure is how far away you are from what the ecu is expecting when the cams aren't advanced. I've read a few times that up to 6 degrees is OK and after that you get the deviation codes, can't say with 100% certainty it's definitely at that figure, but that's what the internet says. There is a cam sensor on each inlet cam, the exhausts don't have one. The advance mechanism and lift adjust are only on the inlet cams. The camshafts "actual angle" reading seems to be set at zero when you start the car and then shows how many degrees the inlet cam advances when activated. The fact both sides are saying 30 when advanced says -The cam adjustment is working on both banks. -The cam sensors must be working - The crank sensor must be working Additionally if there was a problem with either the crank sensor or the camshaft sensors I'd of thought they'd be a code for them and the chance of them both being faulty at the same time seems very low. From what I remember mine only advances when blipped too, so that bit seems normal. Looking at the above I can't see how there can be any other explanation other than your car is timed wrong. I can see however that it's worth deeply researching before facing having to take the engine out again. Personally I'd be phoning people like 9E and asking them (I'd offer to pay for their time and advice) What a pain Mac

As Slutters says it would be good if you could see commanded angle for the cams but having looked through all the parameters available on my durametric I don't think that was there.

Thanks, appreciate your thoughts. I don’t have access to an oscilloscope unfortunately. It does look like it all points to the cams being set incorrectly.

Hi rgracin, I had similar symptoms on my 996TT a while back—cam deviations reading close to yours, along with noticeable noise, especially when VarioCam high-lift was activated. I spent quite a bit of time chasing the issue and documented everything in two threads over on PelicanParts: Cam Position Deviation on 996TT P0021 and Noises I explored just about everything—spun cam sleeves, worn ramps, stretched chains, collapsed tensioners, even intermediate shaft gear separation. But in the end, the root cause turned out to be worn seals inside the cam phasers. I sent my phasers to Chris at Dr. Vanos in Austin, Texas . After a rebuild, the cam deviation readings returned to spec, the CEL and codes disappeared, and the engine has been running quietly and smoothly ever since—even under high-lift activation. In your case, since both banks are showing large and nearly equal deviations (-12.5 and -15), I'd definitely start by verifying mechanical timing. But if that checks out, I strongly recommend inspecting—and likely rebuilding or replacing—the cam phasers, especially if they’re original. The internal seals do degrade with age, regardless of mileage. Happy to share more info, or hop on a call if it’s helpful. Wishing you the best of luck getting it sorted—and hopefully back on the road soon! EDIT: For reference, here’s a great video from Martin Hill that provides a look inside the cam phasers used on 996 Mezger engines. https://youtu.be/aI4rEVEJpJw?si=hjPVm831mv3p28Ev Cheers, Jeff