AOS - Question

[SeanBuller]

We just completed a compression test on all 6 cylinders and they are all reading ~210 PSI.

I have read some things about the camshaft variable timing solenoid. Should i be investigating this solenoid? I heard you can remove it, and apply voltage to them to see if they are actuating. Others mentioned about the VCT sensor?

Any ideas on next steps would be great. We are continuing on Markus' step 1. The oil was replaced a few weeks ago with the recommended Mobil One oil and a new filter was installed.

Thanks,
Sean

[Smallblock454]

Hello SeanBuller,

problem is i don't have a conversion table from Porsche DTCs to OBD2 for the ECU.

This website lists the error P0012 as: A Camshaft Position (CMP) Timing Over - Retarded (Bank 1) P0012 OBD-II Fault Code, Camshaft Position - Porsche

There is a Porsche DTC 112 that says hall effect sensor 1. But that doesn't make sense, because if the hall sensor didn't work, the engine didn't run the way it does.

If somebody has a conversion table for OBDII to Porsche DTC and the 7.2 Motronic maybe i can help with the Porsche DTC part.

Important part before you change sparks is to turn over the engine without sparks, this way you get all oil out if the cylinders.

My problem is the hard knocking noise in the video starting at 00:20. That doesn't sound good. Can you locate where it is / was coming from? Sounds like a valve banging on a piston.

Regards, Markus

EDIT:
If all cylinders have 210 psi – good value, maybe a bit too high.
Noise could be caused by a not properly working hydro.
Don't think it's a solenoid problem of the camshaft adjuster.

[SeanBuller]

Hi Markus,

What do you mean by hydro may not be working properly? Is there any way to test this? Also what exactly is the hydro?

We just cleaned the air intake/throttle body and replaced all spark plugs.

Thanks,
Sean

[Smallblock454]

Hello Sean,

by hydro i mean hydraulic lifter. Sorry, some german to english mistranslation.

You can test hydraulic lifters. To do that you have to remove the camshafts first and than have to remove the hydraulic lifters. To do that you'll need some special tools. So this is more for the advanced DIY mechanic.

If you can hear that the noise is coming from the valvetrain, it might be caused by a valve or hydraulic lifter.

But before testing hydraulic lifters i would recommend to go through all easy to do test steps listed above.

If the noise does come from another part of the engine we have to investigate more into that.

At the moment i would recommend to let the engine run as little as possible and don't rev it up.

Regards, Markus

[SeanBuller]

Thanks for all the help guys, we really appreciate it!

Update:

We cleaned the MAF and air intake (throttle body). There was a fair bit of oil in the tube, not quite a puddle, but it was definitely present. We replaced all of the spark plugs, a couple of them were quite black and have definitely seen better days.

We noticed that one of the hoses going between the intake and AOS was loose, so we believe this is the cause for the rough idling. When we just started the engine up, the idling seemed completely normal and only a little bit of white smoke came out of the exhaust on initial start.

We tried giving the car some throttle (around 1800 - 2000 RPM) and that rattling noise is still present. We are no longer getting any misfire codes, but we are still getting P0012, which is the intake camshaft position over-retarded.

Are you still thinking that it could be the hydraulic lifters? To me it seems possible that it is the timing sensor and/or solenoid?

Thanks again,
Sean

[Gelbster]

P0012 - how much retarded ? Need Durametric for that .Could the the solenoid btwn Exhaust & intake failed?

[Smallblock454]

Hi Sean,

my opinion:

A timing sensor wouldn't cause a mechanical noise like that. The engine would just die.

A bad camshaft adjuster solenoid could cause a wrong timing. But to me it sounds more like a single valve problem than all valves of one cylinder bank or something like that.

Also if you would have a completely bad camshaft timing at one bank you wouldn't have perfect compression in that bank.

But it is always hard to do a diagnosis from a video.

That is why i asked to locate the noise. And that is why i suspect a hydraulic lifter. Because if it fails there must be no negative effect to the compression.

Gelbster's question is also a good one. How much retarded?

Regards, Markus

[Gelbster]

Maybe the retard is because the knock sensor is being activated by the clattering?
Markus - insomnia?

[SeanBuller]

Thanks for the prompt responses!

We do not yet have a Durametric, we will be able to determine how retarded it is once we get that information. It's hard to locate the noise as we are afraid to run the engine for too long. What are your thoughts on running it and holding it at 1800 - 2000 RPM while we locate the noise?

It makes sense to be the hydraulic lifter, but I am confused why the code is showing up saying P0012. Could that just be a red herring?

Gelbster, those are good questions. Unfortunately I don't know enough about engines to answer them.

Thanks,
Sean

[Gelbster]

In theory - and I stress theory! -you could disconnect the knock sensor on that bank and see if the retard goes away.
I would be too timid to do that. I would rather locate the source of the noise. Based on your video, it sounds too loud to be a lifter.One collapsed lifter makes a ticking noise.Your noise sounds 'bigger' like a heat shield/exhaust banging together. Hopefully not a bearing. But a noise generated outside the crankcase would not activate the knock sensor .
Before you start dismantling the engine, please understand this is not a simple task, nor inexpensive. Get skilled,knowledgeable help.The M96 is very unforgiving !

[911monty]

Unless I'm mistaken, the knock sensor only retards ignition timing, not cam timing. Knock is typically due to low grade fuel burning too early in the compression stroke causing detonation and piston knock. Cam timing changes optimize low end torque or high end horsepower.

Seems strange to have good compression, with a severely retarded cam. I might suggest pinning crank at TDC cyl #1, pull the cam plug and see how the timing marks line up. I would expect to see the bank 1 cam a few degrees off. I'd then rotate the crank 360 degrees while observing bank 1 cam and make sure it rotates.

[Smallblock454]

Hello and good morning,

it's now 7:10 in Germany and i'm back. But i have to go to work now.

To test the adjuster solenoid of the camshaft tension element electronically a.f.a.i.k. you'll need a Durametric or PST (Porsche system tester) diagnosis system.

I attached some infos concerning the components and diagnosis. Maybe this gives a better understanding.

I don't agree with Gelbster about the noise. This can be a single valve / hydraulic lifter – believe me, it can be this loud.

The question is why it could fail in a wake of an AOS failiure? Maybe hydrolock. If there was enough oil in the cylinder to prevent the valve to open the hydraulic lifter could be harmed.

Another question. In the video the noise i'm talking about is starting at around 00:20. Is it always the same that the noise comes up some seconds after the engine starts. Or does it sometimes start directly with that noise?

Regards, Markus

[Muskoka Minute]

We are going to get the Durametric to see what this thing is doing.

Now the question is which one can I get away with?

The Enthusiast Kits or the Professional Kits

Please let us know.

Thanks for all the help so far guys.

Cheers!

[911monty]

Originally Posted by Muskoka Minute

We are going to get the Durametric to see what this thing is doing.

Now the question is which one can I get away with?

The Enthusiast Kits or the Professional Kits

Please let us know.

Thanks for all the help so far guys.

Cheers!

The Enthusiast is good for 3 VINs where the Professional allows unlimited VINs. You only need the Enthusiast version. Call Durametric directly and ask if they have any refurbished. Did you pull the green cam plugs and confirm cam timing?

[Muskoka Minute]

Not yet.
I have to do some more research on how to do that.
I'm also going to check the water pump tonight on the off chance.

[Muskoka Minute]

double post

[911monty]

Cam timing is easy to check. No special tools required. Just have to buy the green cam plugs to replace the ones you pull.

edit: AND you don't have to run it to check it!

[911monty]

Originally Posted by Muskoka Minute

Not yet.
I have to do some more research on how to do that.
I'm also going to check the water pump tonight on the off chance.

I don't think that noise is from the WP. My thought is that something Mechanically changed between the crank position sensor and the cam position sensor after AOS failure. Possibly from hydrolock, but first thing you need to confirm is mechanical integrity. Since the CPS gets signal from the flywheel which is bolted to the crank it is pretty safe to assume that didn't change. The mechanical relationship between cams and crank is maintained by cam chains and their tensioners. The cams could have slipped at their adjuster plates or the cam chain tensioner and/or ramp could have failed. Either one of those scenarios would cause the cams to be retarded. However with the noise from the engine, cam chain slop is more likely. Both of these can be visually confirmed or eliminated by checking the cam timing.

[Muskoka Minute]

Originally Posted by 911monty

I don't think that noise is from the WP. My thought is that something Mechanically changed between the crank position sensor and the cam position sensor after AOS failure. Possibly from hydrolock, but first thing you need to confirm is mechanical integrity. Since the CPS gets signal from the flywheel which is bolted to the crank it is pretty safe to assume that didn't change. The mechanical relationship between cams and crank is maintained by cam chains and their tensioners. The cams could have slipped at their adjuster plates or the cam chain tensioner and/or ramp could have failed. Either one of those scenarios would cause the cams to be retarded. However with the noise from the engine, cam chain slop is more likely. Both of these can be visually confirmed or eliminated by checking the cam timing.

I'm going to check/adjust the camshaft timing tonight.
Can this be done with the spark plugs in?
or do they have to be removed? or does it just make it easier with them out


On a side note...
I found a used Durametric - Professional for $575 US plus shipping....
Seams like a lot of money...

I don't know what to do?
How imperative is it to have one?

[911monty]

Originally Posted by Muskoka Minute

I'm going to check/adjust the camshaft timing tonight.
Can this be done with the spark plugs in?
or do they have to be removed? or does it just make it easier with them out


On a side note...
I found a used Durametric - Professional for $575 US plus shipping....
Seams like a lot of money...

I don't know what to do?
How imperative is it to have one?

Finding TDC is much easier with the spark plugs out. An easy method to determine TDC on the bank you are on is about 180 deg before TDC (pin location on crank) place something finger, palm etc. over the #1 cyl plug hole (you can even use your compression tester). Then rotate to TDC you will feel/hear the air escaping if you are on the correct cylinder (Rotate crank 360 degrees to check bank 2). DO NOT ROTATE CRANK BACKWARDS.

Personally I would wait on the Durametric until you confirm cam timing. And I see no reason to purchase a professional version unless you plan on advanced application such as writing/changing code to the DME. The Enthusiast will do everything you need to do and is new from Durametric for around $285.00 and is good for 3 cars and maybe more.
Again my .02 cents. Now where are the experts??? JFP, Jake I'm absolutely certain they have experienced failure modes due to failed AOS.