Does anyone know why camshaft deviation angle, as read by a Durametric, is an indicator of engine health? Supposedly it is the deviation between the camshafts and the crank.

I read somewhere a while back that the acceptable range is 0°-6° total absolute value of the two camshaft deviation angles with 0° being perfect and 6° at the upper limit.

Is it an indicator of how much the timing chain has stretched? Can anyone chime in on this?

 

I don't know the values but an important thing is to get a reading change and equal on both side. This is because of the weakness of a seal on the camshafts. The oil under pressure coming from the camshaft solenoid is normally going to the vario cam to advance the cams. But if this seal failed there will be a malfunction of the vario cam. Look at the post from Porsche Doc about this failure: http://forums.rennlist.com/rennforum...e-p1325-2.html

 

jpflip, your thinking the "Actual Camshaft Angle" which at idle is 0° and advances to 30° over a certain RPM. I'm talking "camshaft position deviation" which stays pretty much constant. There is a slight change once the engine is warmed up.

 

Sorry Pmafia you're right. Camshaft angle was what I was loging and not deviation.... I will definitively learn something from this question. Let's hope somebody will get an answer...

For a Boxter but JFP explanation is interesting...http://forums.pelicanparts.com/boxst...deviation.html

 

jpflip, that explanation does make sense. I would think it would have something to do with the timing chains. Just for information purposes my camshaft deviation angle for bank 1 was 0° and for bank 2 was -.9°, the car has 60k miles. Looks really good to me from what I have seen. Lets hope someone experienced engine builders can offer some input so we can both learn something.

 

Always like to read that kind of information. Thanks for starting this subject Pmafia! We learn something new every day ;-)

 

Some info in this recent thread about camshaft deviation

https://www.6speedonline.com/forums/...n-minutes.html

Rennfabbs car was showing 11 degree deviations after a mistake timing the cams and this was enough to throw codes and prevent the cam advance system working.

And

 

^^^ In that thread, I think winnigt2 hit it right on the head.

"a large deviation shows either timing chains lengthened or cam shaft sensor not in order"

 

Every motor I have taken apart I have in stalled the cam plates and check the timing before dis assembly. Not one was on the money. 5000 mile motor right out to 80,000 miles. My motor never changed after install by no matter how much time you spend on timing the cam they never end up dead on. It must be something with the intake vario sprocket having some lose tolerances.

 

+1 to what Tim said. Used to own the factory tooling (thieves!!!!) and do remember after discussions with him that I too never found one motor to be dead on during service work.

My post(linked about) definitively showed that the cam deviation of ~11 degrees per bank was sufficient to throw the codes. The DME referenced this deviation immediately and put the variocam into a state of shutdown. The large deviation was caused by the crankshaft not being in proper relation to the camshafts(proper TDC) before the cam bolts were set to their pretorque of 22ftlbs. Subsequently re-timing the cams resulted in cam deviations of less than a 1/4 of a degree(.02 and .08 degrees at warm idle actually). This being set via TDC indicator and a degree wheel looking for actual piston dwell.

Camshaft deviation should not change anything more than a few tenths of a degree. The cams are physically friction locked in this position. They will deviate a very tiny bit based on pressure application of the hydro tensioners as the oil warms, oil pressure drops, and as the overall dimensions of the motor change as it warms up.

Major deviation could indicate one of many possible mechanical failures from stretched/broken chains, failed chain ramps(sliders) or tensioners, slipped cam gears, sheared key on the crank IMS, etc, etc.

 

hi
i drive a 996 c4 3.4 2000 190000km

post rough idle I had the fault code 174 (p1341).
and the actual values when the engine was off.
cam pos devi. bank 1 -9.12°
cam pos devi. bank 2 0°

after some research I deleted the faul code and started the engine again
the cam pos deviation on bank 1 was initially 0° and the actual value -10.5.

after high revs (4000rpm)
the the cam pos dev. changed to -9.12 and the actual value around 0.2
the actual value changes to around 27° at 2000 rpm. (variocam activation)

With increasing oil temp. (94°C) the cam dev. decrease to 8.7°
the variacom is not anymore activ and the error is p1341 is shown.

it seems that the variocam control is working properly
the camshaft positon values seems consistant
the decrease from 9.12 to 8.7 is probably due to thermal expansion and the lower viscosity of the oil in the hydraulic valve lifter.

the engine sounds cold and after heating up in idle nominal
the rough idle and the scary tiking noise was present after a 300km ride.

any remote diagnosis are welcomed

 

In the NA 996 engine excessive cam shaft timing deviation can be a sign of cam chain/tensioner problems or a failing IMSB. However, I note you drove 300km so if the IMSB is failing it is one of the slowest to develop ever.

My advice is to be safe you should get the car to a qualified tech for a diagnosis. In the meantime the less you run the engine the better. In fact no running at all is best. If the engine has to be run let it be under the supervision of the tech as he diagnoses the cause of the noise/rough idle.

One thing you can do if you are feeling frisky is remove the oil filter housing and let the oil fall into a spotlessly *clean* drain pan. If you find ferrous metal bits -- fine bits -- in the oil or filter folds that's not good. Hard plastic bits can be from a deteriorating chain guide cover. Pale green rubber like bits can be from a failing tensioner piston o-ring.

 

hi thanks for the fast Respons

190000 km are a lot, isn't it?
I don't want spent a fortune, and honestly i do not have very promising experiences with my dealer

what surprise me ist that the cam deviation lead to a error and the deactivation of the variocam but the engine warning light is not on.

sad, that the 2000 year model has only one cam sensor. it would be helpful to know if both banks are misaligned. Otherwise we could se if it's only on one bank or both (IMSB).

I haven't had any drops of oil below the interface to the gearbox, so the sealing seems to be ok, which doesn't mean that the bearing must be ok. What seems to be strange, is that the engine sounds now ok, and the unstable idle is gone. If the IMSB would be damaged the phenomena should be present continuously, isn't it?

 

190000km a lot? Hardly. 'course, you're talking to a guy who has 477000km (297K miles) on his 2002 Boxster.

Sorry but I missed the "P1341" error code.

P1341: 174 Camshaft Adjustment, Bank 1 - Signal Implausible, 174 Camshaft Adjustment, Bank 1 - Below Limit, 174 Camshaft Adjustment, Bank 1 - Above Limit.

That's not a failing IMSB or even failing cam chain guides, tensioners, that's a failing (failed) VarioCam solenoid/actuator. My 2002 Boxster went through this at around 250K miles.

The fact the engine sounds ok now and is running better is not that odd and doesn't mean there is not a serious problem. Again with my 2002 Boxster, it was running poorly and the idle was going up and down, way down, way lower than it should have been down in the "500" range. At some point I turned the engine off then restarted it and the symptoms were gone. They didn't return the 30+ mile drive home. They were not present at engine start the next business day when I drove the car to the dealer -- just a mile or two away though.

I think in the case of your car you are a bit fortunate in that IIRC -- this is 2nd hand info -- you can replace the VarioCam solenoid pretty easy without having to open up the engine.

If you do not want to take the car to a dealer or a qualified indy shop to have the car diagnosed and repaired you can consider replacing just the solenoid. Do more research before you start out to know what you are getting into. Be aware the camshaft bolts should not be reused and the camshaft cover has to be resealed to not only avoid external oils leaks but internal ones that allow high pressure oil to leak out and thus possibly allow the valve gear to run with less oil pressure and supply than it would normally have. Not good.

If the symptoms are gone after the solenoid R&R and don't return then it was just solenoid. But if the symptoms come back it is the actuator and this is more work to replace. The camshaft cover has to come off and the cams have to be removed. They have to be installed again and with the proper timing. The camshaft cover must be resealed and this doesn't mean one slops a lot of sealant on the sealing surfaces and tightens the bolts down until the excess squeezes out. It is more involved than than. This is not a job for the typical DIY'er.

 

hi

The "specialist" exchanged the worn out guiding plated on the variocam actuator. But the error occurs still. I recorded some signals from the DME yesterday.




Is it the IMS Bearing? which makes the readings so unstable?

KR