Camshaft Position 1 Deviation of -8.97

[xmac]

Car in question: 1999 C4, M96.02, 41k miles (had it since 20k miles), original/stock IMS bearing

Alright, so I stumbled on some posts regarding durametric readouts for camshaft deviation to check into the health of the IMS. I remembered I logged a bunch of real-time parameters back in 2012 just to establish a baseline with my new Durametric tool at the time. I finally found my old hard drive with the data and to my surprise, my camshaft position 1 deviation read -8.97 cold at idle and varied down to -9.53 when driving around. Camshaft deviation, position 2 is solidly at -3.19 regardless of engine speed. On another post, I read that the durametric software may have had issues logging this parameter at the time.

No CELs, no logged errors, been running fine for the last three years, and yes, I drive the snot out of it. When I cut the oil filter I find the random tiny shards brown plastic from the variocam guides. I have a magnetic drain plug and have only seen a light amount of the typical fine metal on it. The previous owner kept meticulous records of all work done at the dealer, and no major engine work was ever done other than oil changes. I found a post about a potentially bent sensor plate on the cam where the engine is correctly timed but the sensor is reading the parameter incorrectly??

My thought at the moment is to not drive the car, pop the green plugs and check timing as well as pulling the sump pan for inspection. I also plan to log the camshaft deviations this week with the newer version of the software and see what I get. Assuming I get the same numbers, I have some questions:

1. Since the position 1 is moving around a little bit between running and idle (~0.78 degrees), should I start having my heart attack now?

2. If the timing is off by this amount, is it a simple re-timing of bank 1 if all else looks OK?

3. Dumb question also is how much timing adjustment can be made since the sprocket appears to have large slots for adjustment?

4. Another dumb question is if bank 1 skipped a tooth, would I know it already?

5. Should I just open up the bank 1 valve cover to inspect/replace the variocam pads? (trying to do the least invasive first)

6. Anything else to check/do?

Thanks for reading.

[JFP in PA]

Car in question: 1999 C4, M96.02, 41k miles (had it since 20k miles), original/stock IMS bearing

Alright, so I stumbled on some posts regarding durametric readouts for camshaft deviation to check into the health of the IMS. I remembered I logged a bunch of real-time parameters back in 2012 just to establish a baseline with my new Durametric tool at the time. I finally found my old hard drive with the data and to my surprise, my camshaft position 1 deviation read -8.97 cold at idle and varied down to -9.53 when driving around. Camshaft deviation, position 2 is solidly at -3.19 regardless of engine speed. On another post, I read that the durametric software may have had issues logging this parameter at the time.

No CELs, no logged errors, been running fine for the last three years, and yes, I drive the snot out of it. When I cut the oil filter I find the random tiny shards brown plastic from the variocam guides. I have a magnetic drain plug and have only seen a light amount of the typical fine metal on it. The previous owner kept meticulous records of all work done at the dealer, and no major engine work was ever done other than oil changes. I found a post about a potentially bent sensor plate on the cam where the engine is correctly timed but the sensor is reading the parameter incorrectly??

My thought at the moment is to not drive the car, pop the green plugs and check timing as well as pulling the sump pan for inspection. I also plan to log the camshaft deviations this week with the newer version of the software and see what I get. Assuming I get the same numbers, I have some questions:

1. Since the position 1 is moving around a little bit between running and idle (~0.78 degrees), should I start having my heart attack now?

2. If the timing is off by this amount, is it a simple re-timing of bank 1 if all else looks OK?

3. Dumb question also is how much timing adjustment can be made since the sprocket appears to have large slots for adjustment?

4. Another dumb question is if bank 1 skipped a tooth, would I know it already?

5. Should I just open up the bank 1 valve cover to inspect/replace the variocam pads? (trying to do the least invasive first)

6. Anything else to check/do?

Thanks for reading.

OK, the spec for that car is +/- 6 degrees, so the deviation value does indicate that you are somewhat out of spec. If the engine had jumped time, it would be well more than 8-9 degrees out, so I do not think that is your issue, especially as yours is a five chain motor. I am also not aware of the Durametric software not being able to correctly read these values, but having said that, I need to ask what version of the software are you using?

It is entirely possible that this level of deviation is the result of wear on the VarioCam components (tensioners, chain paddles, etc.). Before you start pulling cam covers off, you need to understand that doing so requires cam retaining tools as the cover is one half of the cam journals holding the cams in place. I think you need to have the cam system examined by a shop with both the equipment and knowledge required to properly access the situation. You are probably in the market for some replacement components and a retiming for the cams.

[xmac]

JFP,

Thanks for the quick post and guidance. The original hard drive died but it would have been 6.2.1.1 or older. Fairly certain it is not a software glitch but I will use the new 6.3.2.5. Thanks for the warnings since there are certainly people in this virtual world that can get themselves into trouble and in over their head quickly. I know reading posts/manuals and watching youtube videos does not make an instant mechanic. I am certainly a newbie to P-cars but not to taking cars/engines apart since I do all of the maintenance and repairs on my cars for enjoyment. (picture of some fun work I did on my BMW V8 last year below)

Hopefully, I know what I am getting myself into. I already ordered some parts in preparation and am shopping around for the special tools (Cam holders, cam timing, and either the long threaded bolt for the variocam actuator or heavy duty zip-ties as Wayne at Pelican used.

[Silver_TT]

especially as yours is a five chain motor

JFP - Everything you stated makes perfect sense and is good guidance. I was wondering if you could you say a little more about your quote above. Thanks in advance.

[JFP in PA]

_{especially as yours is a five chain motor}

_{JFP - Everything you stated makes perfect sense and is good guidance. I was wondering if you could you say a little more about your quote above. Thanks in advance.}

_{Sure, the M96 engine came in two timing chain configurations, the three and five chain. The earlier engines (before 2003), all M96 engines had a five chain layout on the cylinder heads where a chain came up from the IMS shaft to one of the two cams, and then a separate chain ran from one cam to the other:}

With the small chain running between the two cams, it is actually fairly difficult for these engines to jump cam timing, even under adverse conditions. On the later engine's, the chain between the two cams was eliminated, and the chain coming up from the IMS shaft went around both cams on each cylinder head, reducing the number of chains from five to three. The three chain design, while simpler and making more room for the VarioCam+ hardware, was more prone to jumping time (usually on one cam) under adverse conditions because the mechanical link between the cams was now missing.

[xmac]

As expected, with the latest 6.3.2.5 version, here is the screenshot. Solid -9.27/-3.22:

Edit: added Durametric software revision

Edited March 6, 2014 by xmac

[JFP in PA]

As expected, with the latest 6.3.2.5 version, here is the screenshot. Solid -9.27/-3.22:

Edit: added Durametricc software revision

At least the values are steady, which is a good thing. The next question becomes why the car is out of spec. Normal suspects (as mentioned) are the tensioners and chain paddles, including the ones on the short chain between the two cams, which are often the problem on the five chain cars.

[xmac]

OK, TDC Bank1, exhaust cam plug removed. Doesn't look like 9 degrees off.

I used some special software to try to visualize a 9 degree offset angle:

Edited March 7, 2014 by xmac

[Ahsai]

The deviation is 9.27 degree of the crankshaft. I think the cam deviation will only be half of that but still I agree though your exhaust cam notches seem to line up perfectly. I think maybe the reason is the cam sensor (used to compute the deviation) is detecting the reluctor ring on the intake cam so this deviation may be due to the intake cam not aligned due to variocam pad wear? Do the intake cam notches also align with the cam cover? Just my guess...

Edited March 7, 2014 by Ahsai

[JFP in PA]

Couple of points: It is very difficult, even with software, to envision what 9 degrees looks like. Second, the deviation is with the engine running, not static, so standing still it can look different than expected.

The test you should try is to insert the cam locking tool with the engine locked at TDC, if the tool slides right in, the cams are fine, if it does not go in easily and bolt down without effort, the cam is off:

[xmac]

Couple of points: It is very difficult, even with software, to envision what 9 degrees looks like. Second, the deviation is with the engine running, not static, so standing still it can look different than expected.

The test you should try is to insert the cam locking tool with the engine locked at TDC, if the tool slides right in, the cams are fine, if it does not go in easily and bolt down without effort, the cam is off:

Points well taken. I am of the opinion that if something seems wrong, (in this case the Durametric readings) it probably is. Will do the cam lock test over the weekend.

[JFP in PA]

Couple of points: It is very difficult, even with software, to envision what 9 degrees looks like. Second, the deviation is with the engine running, not static, so standing still it can look different than expected.

The test you should try is to insert the cam locking tool with the engine locked at TDC, if the tool slides right in, the cams are fine, if it does not go in easily and bolt down without effort, the cam is off:

Points well taken. I am of the opinion that if something seems wrong, (in this case the Durametric readings) it probably is. Will do the cam lock test over the weekend.

Be aware that the cam can be in the correct position at rest, but out of spec running if the hydraulic tensioner system or shoe wear pads are bad.

[xmac]

The deviation is 9.27 degree of the crankshaft. I think the cam deviation will only be half of that but still I agree though your exhaust cam notches seem to line up perfectly. I think maybe the reason is the cam sensor (used to compute the deviation) is detecting the reluctor ring on the intake cam so this deviation may be due to the intake cam not aligned due to variocam pad wear? Do the intake cam notches also align with the cam cover? Just my guess...

Thanks for the reminder. I read some posts on the halving the angle.

As far as I am aware, there are no notches to reference under the other plug, hence the shorty cam lock tool. The other end of the intake cam (flywheel side) would just point outboard with a single notch vs. the half moons to denote TDC on Bank1.

[Ahsai]

The deviation is 9.27 degree of the crankshaft. I think the cam deviation will only be half of that but still I agree though your exhaust cam notches seem to line up perfectly. I think maybe the reason is the cam sensor (used to compute the deviation) is detecting the reluctor ring on the intake cam so this deviation may be due to the intake cam not aligned due to variocam pad wear? Do the intake cam notches also align with the cam cover? Just my guess...

Thanks for the reminder. I read some posts on the halving the angle.

As far as I am aware, there are no notches to reference under the other plug, hence the shorty cam lock tool. The other end of the intake cam (flywheel side) would just point outboard with a single notch vs. the half moons to denote TDC on Bank1.

Makes sense. I forgot that the 3 chains engine cams are like that. My point of the cam sensor (blue arrows) picking up the position of the INTAKE cam instead of the exhaust should still makes sense. That is, the sensor will pick up any exhaust cam deviation + any slop at the varaiocam chain and report the total. So it's possible even if your EXHAUST cam notches are perfectly aligned, there could still be slop introduced by variocam (due to worn saddles) that gives you a net deviation.

Edited March 7, 2014 by Ahsai

[JFP in PA]

The deviation is 9.27 degree of the crankshaft. I think the cam deviation will only be half of that but still I agree though your exhaust cam notches seem to line up perfectly. I think maybe the reason is the cam sensor (used to compute the deviation) is detecting the reluctor ring on the intake cam so this deviation may be due to the intake cam not aligned due to variocam pad wear? Do the intake cam notches also align with the cam cover? Just my guess...

Thanks for the reminder. I read some posts on the halving the angle.

As far as I am aware, there are no notches to reference under the other plug, hence the shorty cam lock tool. The other end of the intake cam (flywheel side) would just point outboard with a single notch vs. the half moons to denote TDC on Bank1.

Makes sense. I forgot that the 3 chains engine cams are like that. My point of the cam sensor (blue arrows) picking up the position of the INTAKE cam instead of the exhaust should still makes sense. That is, the sensor will pick up any exhaust cam deviation + any slop at the varaiocam chain and report the total. So it's possible even if your EXHAUST cam notches are perfectly aligned, there could still be slop introduced by variocam (due to worn saddles) that gives you a net deviation.

Drawing1.jpg

In these systems, there are several ways for the deviation to be out of spec, which is why you have to take it apart and look for something obvious, like worn pads, a loose chain, etc. Always a fun project............

[Ahsai]

The deviation is 9.27 degree of the crankshaft. I think the cam deviation will only be half of that but still I agree though your exhaust cam notches seem to line up perfectly. I think maybe the reason is the cam sensor (used to compute the deviation) is detecting the reluctor ring on the intake cam so this deviation may be due to the intake cam not aligned due to variocam pad wear? Do the intake cam notches also align with the cam cover? Just my guess...

Thanks for the reminder. I read some posts on the halving the angle.

As far as I am aware, there are no notches to reference under the other plug, hence the shorty cam lock tool. The other end of the intake cam (flywheel side) would just point outboard with a single notch vs. the half moons to denote TDC on Bank1.

Makes sense. I forgot that the 3 chains engine cams are like that. My point of the cam sensor (blue arrows) picking up the position of the INTAKE cam instead of the exhaust should still makes sense. That is, the sensor will pick up any exhaust cam deviation + any slop at the varaiocam chain and report the total. So it's possible even if your EXHAUST cam notches are perfectly aligned, there could still be slop introduced by variocam (due to worn saddles) that gives you a net deviation.

Drawing1.jpg

In these systems, there are several ways for the deviation to be out of spec, which is why you have to take it apart and look for something obvious, like worn pads, a loose chain, etc. Always a fun project............

Makes sense.

[xmac]

OK, so I was off 360 degrees since the cam tool did not fit it (I was at TDC Bank 2), spun it another 360 and the cam tool fits perfectly without any resistance or wiggling. Ahsai, 10-4 on the reluctor info. I found the post where the reluctor may have been bent causing 12 degree deviation, but the engine was not opened up afterwards to see what was wrong.

Maybe it is obvious to others, but I realized today that the "1/2" moon markings on this exhaust cam are not centered/symmetric:

Edited March 8, 2014 by xmac

[xmac]

So, after finally getting a correct cam timing tool, I was able to get the cam pads and cam-to-cam chain swapped on Bank 1-3 along with the newer version of the 1-3 main chain tensioner. While waiting for the tool, I opted to do one more pre-failure directive and pull the sump plate. Although it was no yard sale, the sump pickup still had some minor debris. All in all, much easier than I expected. Looking at the wear on the pads and where the oil weep holes in the pad were clogged with broken plastic bits, I'll likely replace Bank 4-6 this summer.

Edited April 9, 2014 by xmac

[Hobbes]

It looks like I am having similar issues as described in this thread. I have a 2000 996 C2. I'm using the Durametric v6.3.2.5 and I looked at the deviation values as well as actual angle values for the camshaft.

Camshaft position 1 deviation: -11.48

Camshaft position 2 deviation: -5.03

Actual angle for camshaft bank 1: -0.30

Actual angle for camshaft bank 2: -0.34

I did have fault codes, P0410, P1411 and P0507. These codes are unrelated to the camshaft issue and relatively easy to fix, but the camshaft issue has me scratching my head. What prompted me to search on this is an audible knocking coming from the engine. Similar to the sound a lifter would make rapping back and forth. From what I am reading, taking the engine out and replacing worn parts is imminent in the foreseeable future. Before I roll up my sleeves and drop the engine, is my first course of action to get the cam tool and perform the actions in xmac's #17 posting? Or, based on the deviation values, I can pretty much assume age has taken its toll and the parts need replacing?

Thanks,

Ken

[JFP in PA]

It looks like I am having similar issues as described in this thread. I have a 2000 996 C2. I'm using the Durametric v6.3.2.5 and I looked at the deviation values as well as actual angle values for the camshaft.

Camshaft position 1 deviation: -11.48

Camshaft position 2 deviation: -5.03

Actual angle for camshaft bank 1: -0.30

Actual angle for camshaft bank 2: -0.34

I did have fault codes, P0410, P1411 and P0507. These codes are unrelated to the camshaft issue and relatively easy to fix, but the camshaft issue has me scratching my head. What prompted me to search on this is an audible knocking coming from the engine. Similar to the sound a lifter would make rapping back and forth. From what I am reading, taking the engine out and replacing worn parts is imminent in the foreseeable future. Before I roll up my sleeves and drop the engine, is my first course of action to get the cam tool and perform the actions in xmac's #17 posting? Or, based on the deviation values, I can pretty much assume age has taken its toll and the parts need replacing?

Thanks,

Ken

You need to make sure you are taking your readings after the car is warmed up and driven a bit. Checking as Xmac did will not harm anything, but as your engine is also a five chain, it is a reasonable assumption that the same tensioner wear pads are on their way out. This is a fairly common maintenance problem on these engines.

[Hobbes]

Thanks. The car was warmed up but not driven during the durametric hookup This is my daily driver and was driven less than an hour prior. I did put RPMS on the car during the test and the values I mentioned did not fluctuate. From what I read, this rules out a catastrophic issue associated with an IMS failure; but I also know these cars are prone to IMS failures. (I've already replace the RMS)

[JFP in PA]

Thanks. The car was warmed up but not driven during the durametric hookup This is my daily driver and was driven less than an hour prior. I did put RPMS on the car during the test and the values I mentioned did not fluctuate. From what I read, this rules out a catastrophic issue associated with an IMS failure; but I also know these cars are prone to IMS failures. (I've already replace the RMS)

As long as the engine was thoroughly warmed up, the data should be accurate. While the one cam obviously exceeds the spec limits, as long as the values are constant and not bouncing around excessively, it is not an IMS issue.

On the subject of IMS refits, when Jake Raby gets one of these cars into his shop for a retrofit and it is throwing large deviation values, he will not do the IMS unless the tensioners are corrected as well as he knows the car will eventually throw codes due to the worn pads and does not want anyone to relate the cam deviation issues with the IMS refit.

[Hobbes]

Thanks for the last input. I did not want to tackle the IMS issue. if correcting the deviation has positive results, then I'm steering clear until I absolutely have to.

[xmac]

OK, proof is in the pudding:

I just filled up with DT40, cranked for 10-15secs with the fuel pump fuse out to start building oil pressure, then took the car out for a run. When I first started logging the cam deviation values, the deviation was at the same prior -9.27 value. My first thought was that it was a lot of work for nothing.

Of course all sorts of things started going through my mind as to what else it could be. Then I turned around and looked at the laptop, and the value had dropped to -7.56 and then to -7.53. I noticed that every time I sat at a light idling, the value kept dropping. At the end of a 20 minute run, it dropped down to -6.19, then -6.13 as I sat in the driveway. I supposed it will continue to drop the more miles I put on it.

Although it is at the upper spec, at least I am in the "normal" range. The engine seems much quieter and smoother now at idle too. I'll put some miles on it and probably change the 4-6 cam pads this summer, then consider the IMS bearing.

[xmac]

Here are some updated pictures of the old cam pads with only 41,000 miles on them.