Cam deviation -7.9

Hi guys, I purchased a 996.1 (3.4 MY 2001) approx 1 year ago from a very reputable indie specialist (located 400 miles away) and had a PPI and borescope completed prior to purchase. At this point I must admit, I my engine and automotive knowledge is limited but I was keen to learn. Anyway, PPI came back very good on the whole apart from one observation which was downplayed as very minor and frankly I misunderstood the observation. It was observed that the cam deviation was -7.9, which after discussion with PPI specialist, I misunderstood was related to timing and could be simply rectified by indie prior to sale which I requested. PPI specialist indicated that the IMS bearing had been replaced with an LN Engineering bearing previously by the indie himself, and that this observation was highly unlikely to be an issue or manifest any problems in the future. I accept responsibility for not fully understanding this potential issue. Anyway, fast forward a year, I have developed an oil leak recently which seems minor but has now started to drop on to my driveway, which is on about a 30 deg angle if this is of any relevance. I have also observed a bit of an engine rattle/grind, which seems more prevalent when the engine is hot. Having done more investigation, I'm starting to wonder whether this cam deviation has been related to chain tensioners and/or cam guides, which may explain the deviation and the rattle, although maybe not the oil leak. The car is due a service soon, and I'm going to ask a local specialist to check the oil to understand if any bits of cam guides may be in there, and whilst he's at it change the chain tensioners and measure cam deviation. Would there be any other items or typical component issues that should be checked out that may be leading to the cam deviation and/or engine rattle? Regarding the oil leak, I guess I'll just need to ask him to clean up as best possible and try to understand where it may be coming from. Ultimately, if this leads to an engine out job, in addition to replacement of the cam guides, is there anything else you would suggest should be done, like AoS? Clutch, IMS and RMS have been done in last few years. Thanks, K!

I would drop the sump pan like you state and inspect the bottom of the pan and oil pick up. After that you could install the updated cam chain tensioner for the 5 chain (there are 3 of them), they are slightly longer and may (may) help correct the chain tension a little. I would however, get the guides done asap if I was you. If you have an early 3.4 you are not getting a reading of bank 1 and bank 2 individually so you may have a lot of deviation that is not being read. I would suggest getting the pads and a variocam solenoids done with the info you have shared. UAOS, IMS, RMS,Clutch, Oil scavenge pump, oil dip stick tube, the list goes on for upgrade/maintenance.

Is there any signs of "cam deviation" that one should look for? I have 112k on my 01 c4 and wondering if there are signs that I should be watching for? Last oil change there was a real small piece of plastic in the oil pan which leads me to believe the tensioner is probably braking off......I will be changing the oil again soon to see if I have anymore particles in it but the car runs perfect as is.....

OK. 1) Stop driving it. 2) Drop engine, remove gearbox 3) Replace Cam Variator Actuator, chain rams. Alternatively, you can rebuild the variator actuator. Although, that is OK for a DIY. If I were a pro shop, I certainly would not do a rebuild (which amounts to replacing the seals). 4) Replace RMS, inspect IMS seals. If the leak is coming from the IMS, you should replace the IMS bearing. 5) With the car now 23 years old, you might want to replace the three chain tensioners and all the chain ramps you can get to without splitting the case (4 of the 5, plus the four pads on the actuator) Should have done something about the -7.9 degree deviation when you were buying the car.

@Viper1000 I'd buy a durametric for a start and monitor deviation. I have found pieces of chain guides in my sump before but I only have 3 degrees of deviation. The IMS health, cylindrical run out of the intermediate shaft, the chain pads, and the belt tensioners all play in. Hard to say. Monitor for noise initially then get a durametric.

Quotes source post: 19662222

Agreed. -7.9 is very bad. Jake Raby says stop driving anywhere about +/- 6 degrees.

Quotes source post: 19662362

I don�t totally agree. Yes the spec is 6. However, every .1 out there that hasn�t had the chain guides done is probably over 6. The vast majority of owners are totally oblivious. Catastrophic failures due to the plastic guides are very rare. Mine was -9 on bank 1, the guides were heavily worn but still intact and no CEL. Im glad I did the job, but I probably could have got another 20k out of them or maybe longer. OP should look at his engine due to the leak and noise. Cam dev of -7.9 would be, to me, secondary.

Hi guys, Some very helpful responses, thank you. You are right, I should have tried to better understand the cam deviation at purchase, the person that completed the PPI (which is a very reputable company) largely waltzed past the issue and gave me a confidence that there shouldn't be any issues as IMS had been changed. This was my mistake, and I will literally pay for it now, I understand that, a lesson learned.

*deleted, duplicate post*

Quotes source post: 19662441

Thank you for this response, I was beginning to get worked up by the cam deviation, more so than the leak and rattle, although the latter may be related I guess. I will get it into a local-ish specialist anyway for inspection and take it from there, at least I feel I have some basic information to familiarise myself with the topic and hopefully be able to have a meaningful discussion and make a pragmatic decision when the time comes. At this point I feel like do what I can with engine in (2 of the 3 tensioners, identify and fix leak if possible) and then monitor. If the above isn't feasible or in the end the engine needs to come out, then seek to address all tensioners, cam guides plus potentially replace AoS.

All 3 tensioners can easily be done with the engine in the car. Also remember that these motors have chain rattle no mater what u repair. Its a function of have 5 chains spinning at mach 1 . What scanner r u using to get the cam #s?

If he has a 3.4 5-chain, tensioners are one thing, but for pads, it�s 4 tensioner pads. And yes, can be done with the engine in the car. For the pads, it can be 7-9 hours of work though because you have to take both valve covers off, oil scavenge pumps, exhaust (broken bolts are possible), etc. What you are looking for with worn tensioner pads is dark brown plastic bits in the oil / oil filter. You might see this in the pan as well. If Durametric shows -7, it�s probably the pads. Remember to do top and bottom (2 side to each bank).

Thanks again guys, very useful. I mentioned cam guides, but I also see people referring to tensioner pads and chain ramps, is this all just difference terminology for the same part or are you referring to a different part? I guess a diagram would make things easier but appreciate nobody may have one.

Quotes source post: 19663233

you can download the parts catalog here https://www.porsche.com/australia/ac...artscatalogue/ it has diagrams. Has helped me lots

Quotes source post: 19663233

Chain tensioners - (small pistons) there r 3, ims chain and the l & r long chain chain ramps - the pads for the long chains (can be swapped without splitting engine but engine needs to be out) Chain (variocam) tensioners pads (i guess could also be called cam chain guides)- located on the variocam actuators and tension the 2 short chains. Usually why the cam deviations degrade. These can be done with engine in with a skilled mechanic but would highly reccomend engine out.

^^ This

I think the IMS tensioner / chain ramp is the one that cannot be replaced without splitting the case on the 5-chain engine, correct?

Quotes source post: 19665807

correct. Other large chain ramps can be replaced, however I question the utility of this as I and other owners have been able to get back to spec without replacing these. They don�t appear to impact cam deviation and they are quite large and unlikely to wear through, at least based on my research and observation. On my engine there was some wear but none of the visible pitting that affects the small cam chain pads.

Quotes source post: 19665854

Sorry for the stupid question but then why do they fall apart? Is it a different one?

Quotes source post: 19665860

They just wear over time. You�ll see the center groove. When you look at them side-by-side w the cam pads you can see how much larger the surface area is and how the wear pattern is different as a result. The four cam pads pit as they are smaller and under dynamic tension as the variocam actuator does its thing. Theory that the original material was inferior and new pads are better, unsure how accurate that is. also you can�t visualize the IMS chain pads, so those I can�t speak to, but as noted there�s no way to access anyway. They are smaller and potentially a debris source. Nothing a mortal can do anything about without $$$.

Quotes source post: 19665860

Those longer guides for the long chains and ims chain r a guide for the chain slack to ride against. The chain tensioners keep the chains tight. On the 2 small chains, variocam (can timing) the pads on the actuators push on the chain itself to create tension. This is why they wear faster and chunk.