Variocam Plus Diagnostics

[vizor]

Car is a '07 Cayman S and I started inspecting the two variocam plus solenoid/actuators first with the Durametric and then later with my multimeter. The valve timing solenoid read 10.7 ohms while the valve lift solenoid read 12.7 ohms. Readings from both banks were exactly the same. From old posts concerning the original single solenoid variocam system, I've read the solenoid should read about 13 ohms, but I don't know if that's true for the newer "plus" design. Anyone know? If so, then I guess that points to having two bad valve timing solenoids.

When actuating each with Durametric, what should I monitor and what should I expect? So far I've concentrated on monitoring cam angle. When I actuate the valve lift while at idle it kills the motor, and I haven't tried this at higher RPM yet.

When I actuate the valve timing at idle I don't really hear or feel a change, and only see a small blip on the cam angle plot that drops down from 0 to -250 on the Y axis (what are those units?), however the blip is sometimes much smaller. I'm not sure if that's real (and a problem) or a function of the sample rate. Again, I'm not sure what it should do, should it hold the timing advanced/retarded until I stop it or is just that blip normal?

And in general, is it ok to unplug the electrical connector on all the solenoids and manullay actuate them from a seperate 12V source while the engine is idling?

[logray]

Sorry to not answer these questions direclty, but may I ask...

Why are you troubleshooting your variocam system?

Are there any stored trouble codes? (the DME should throw codes if variocam is not functioning correctly, in which case you would want to carry out diagnostics...)

[vizor]

I haven't found any stored codes yet. Do you know what their resistance should be? I also just applied a 12.67 V source to each solenoid while they are still in the cam cover, engine off. Both lifter solenoids responded with a healthy click, like it had a good amount of force behind it. Both timing solenoids did not, one made no noise at all, and the other clicked so faintly that I really had to concentrate to hear it. Does this sound right for the timing solenoids?

[JFP in PA]

I have to agree with Logray here, if there was a problem with the system, it would throw codes and cause running issues. And knowing how much replacement components cost, I wouldn't be randomly applying voltage to see what happens unless the system is already acting up and throwing codes, you may not like what happens next.............

Edited March 24, 2012 by JFP in PA

[logray]

The car will throw a code if there is a problem 99% of the time.

A better way to check vcam+ operation is to monitor actual angles parameter in durametric.

With a warm engine, monitor the values at idle, then slowly rev the car up to around 4000rpm and you should see them increase to their max value.

[vizor]

It isn't throwing codes yet, but it is acting up. First randomly and over time seems to be more constant. It sounds a lot like a lifter going bad, but I've read a few posts of failing variocam systems mimicking the sound of valve lash, collapsed lifter, etc. I spoke with an indy shop that has diagnosed and confirmed this in a similar fashion, so I thought I would give it a shot before going deeper. Now I'm trying to confirm expected behavoir either through applied voltage or Durametric. Any input would be appreciated.

[logray]

If it is a problem only on one side of the engine swap the actuators for lift and timing between banks. If the problem follows the swap, you've at least cut your chances of whether the solenoids are involved in your problem... and then continue narrowing down...

Perhaps someone with newer literature can provide you with the correct ohm readings for those solenoids.

[vizor]

The car will throw a code if there is a problem 99% of the time.

A better way to check vcam+ operation is to monitor actual angles parameter in durametric.

With a warm engine, monitor the values at idle, then slowly rev the car up to around 4000rpm and you should see them increase to their max value.

OK, thanks. I found this in reference to the 996TT switching points and wondered if it applies to the NA motors and/or changed with the newer models in general. I was trying to figure out if the switching points are purely engine speed based or also a function of load. Anyone have a similar plot a NA vcam+ motor? I'm a bit envious of those with older models as the available information seems much greater. I would love to have the correct ohm readings on hand.

[logray]

Google "variocam primer" for more info on variocam plus.

While the solenoids in the TT might be similar, the variable cam timing systems are different.between the turbo platform and m96/7 platform.

The cayman m97 is a bit of a hybrid between the boxster s engine and 997 engine (both derivatives of the M96), but the info in the variocam primer about variocam plus is very much applicable to your engine. IIRC cayman went to the new DFI design in 2009, maybe just S models though, can't remember.

[vizor]

Over time I have also developed an intermittent hesitation just off idle, this seems to only occur when the engine and ambient is hot. I took some data with Durametric and plotted actual camshaft angle vs nominal and also post processed the data to view it as % error of nominal. I noticed from a dead cold start that both camshafts flucuate in an error band of +/- 20% while trying to maintain the requested angle. From a controls standpoint some level of flucuation makes sense. While cold I believe the valve lift is held to high to accelerate warming of the cats.

When the engine warmed enough to drop the RPM to warm idle, and I believe the valve lift drops to low, I noticed that Bank 2 maintains the +/- 20% error band while Bank 1 now shows a +/- 50% error band. I have always noticed that I do not get any wierd noise or engine behavior during a cold start but only when warm.

When the engine is good and hot, I also sometimes get a buzzing sound around 3200 RPM that appears to come from Bank 1 as best as I can tell. This behavior is intermittent as well and I believe this RPM coincides with when the valve changes lift from low to high. So I drove around and collected data but of course I can't ever get it to buzz while I have my laptop with me. I did notice that Bank 1 does not seem to track the requested cam angle as well as Bank 2 showing poor fidelity when the requested angle is changing direction rapidly, like going from WOT to zero throttle back to WOT.

I decided to try replacing the valve lift control solenoid first. Here's my question. When I removed the solenoid from the cam cover I'm afraid the solenoid body rotated in the bracket and I noticed there is a small notch in the tip of actuator. When I swap solenoids and reinstall, where should that notch be facing? I don't see any obvious marks on the cam cover or in the solenoid bore indicating the required alignment. Thanks.

[Brad Roberts]

Vizor?

Did you figure this out? The vario valve lift doesn't engage until 2800 RPM (give or take a 100 RPM)

[vizor]

Not completely. I swapped in a new valve lift solenoid on one side and then the other, didn't fix the issue so I put the originals back in and kept the new one as a spare.

I also pulled out the valve timing solenoids on both sides and found bits of debris in the finger screen on Bank 1 that keeps trash from flowing into the solenoid (and ultimately the vane cell adjuster). The debris is pieces of very small lightweight spring, my guess is its part of a check valve spring somewhere. I cut open the check valve built into that finger screen but that spring was fully intact, so it didn't come from there although it was the same size.

I was originally planning to just try swapping in a new valve timing solenoid until I found that debris, now I'm hunting where it came from instead. My guess is a chain tensioner but I haven't been able to confirm they have check valves in them and I haven't had time buy the cam lock tool and start pulling them out.

The clacking noise is getting more constant at idle but the car still drives fine, doesn't burn oil, no CEL, nothing. Funny thing is sometimes if I push the clutch all the way to the floor the noise stops completely until the moment I release the clutch again. I can do this over and over again with the same result some days, but other days this has no effect and the clacking keeps on going with the clutch pushed in.