Purchased another 08 supercharged RR for cheap about 2 years ago. Did not move but ran well with crankshaft correlation fault. Front driveshaft broke, easy fix. Correlation fault, not so much. I did hear the chain rattle occasionally, But I decided it was too good to just save for parts, so in we go. Main timing chains were tight, secondary chains looked good as well. Tensioner on bank 1 stuck in collapsed position during a second look 3 days later. Replaced it and retimed the engine. Runs even better now but i still have a correlation fault. I then swapped the timing solenoids to the opposite banks to see if the fault moved with the solenoid, but it did not.
Got my gap tool out and did some comparisons with the other Rover.
"Intake variable camshaft timing" on both banks reads within 5 degrees per bank on both Rovers. "Actual inlet variable valve timing" on the good Rover both banks are the same (0-0.4). On the faulty Rover bank 2 matches the good Rover (0-0.4) but bank 1 reads 9-11 degrees.
Does this point to a faulty camshaft position sensor?

Attached are the graphs that i took from each vehicle.
https://drive.google.com/file/d/1uu8KleuSBdLJXQyMiadj7cq0-FLidDDB/view?usp=sharing
https://drive.google.com/file/d/1DqGWNU90F1wxbjdkeqgwetMbEDuHghjv/view?usp=sharing

Did you replace the cam phasers?

No i did not. Just the sticky tensioner. Chains and guides were all left in place and looked good. I did retime the cams. I do wonder if that is the case. How do i tell if the phaser is trash?
What i dont understand and am trying to figure out is what the signals mean. With only on sensor per bank i would have thought that if the cam sensor is incorrect that the vale timing would also change. but that does not seem to relate. Its like it defaults to a single sensor and changes the timing on both cams together. If you compare the signals from the good Rover to the bad one the cam timing never moves 9 degrees like the questionable signal indicates. It only moves 0-0.4 degrees. Even the cam timing angles only move a few degrees. So I wonder if 9 degrees is even possible without catastrophic engine damage. Also when i unplugged the cam sensor the questionable signal only drops to 5 degrees and not to 0.
Could this be electrickery like a bad ground or something. I am not getting a cam sensor fault only the correlation fault. And also no chain noise since retiming the engine.

I'm not saying this would be a fun job, but might be worth swapping the sensors side to side to see if the issue moves. Pretty clear indication if a sensor is the issue.

I tried swapping the solenoids from one to the other with no change. Unfortunately thats not an option with the cam sensors. I could however take the sensor out of the good Rover to test the signal. BUT:
You got me thinking about the phaser comment, and I remember noticing an anomaly while doing the timing. Before and after resetting the cam timing i noticed that when i turned the engine over the exhaust camshaft would push the intake cam at a certain points and the chain would become slack on the side that should stay tight. However during the rest of the rotation the chain was fiddle string tight. So when i retimed it and saw the loose chain again i simply pushed the guide so the tensioner moved to the next stop. That seemed to solve the issue.
Now that i have spent days watching utube vids on the phasers and learning how the system works. I suspect that the phaser was not locking properly and allowing the exhaust cam to push the intake causing the chain to loosen. And now it is timed in the wrong position which is why its throwing the correlation code.
I also found out that the engine has been replaced when is got into the job. Found a stock number on the front of the timing cover that is not supposed to be there. It is varnished on the top of bank 1 but not equally varnished on bank 2. It also appears that someone may have been in there already since the gaskets were not fully crushed like they should be for the age of the engine. This may have something to do with the phaser being out of time.
So... it looks like Im going back in. At least it will be easier this time now that I know what Im doing. I will open up the phaser to see what i find and decide from there if I clean and reinstall it or replace the lot.

It might take a bit with Christmas and all that, but I will let you know what I find

Definitely keep us posted.

OK here we go...
I went back into the timing chains. Chains were tight and no cam movement. Then I removed the chains and attempted to turn both phasers with the cams locked. Nothing moved. I found that bank 1 oil screen feeding the phaser appeared to be plugged with varnish. So i cleaned it and reinstalled it. Checked the solenoids with the battery for proper movement. They tested good. I then swapped all the sprockets and chains to the opposite bank. It started and ran great. After all that the fault remains. However after clearing the faults it only comes up once the throttle is depressed. I decided to start the graph recording before starting the engine and the one sensor seams to read 0 until the throttle is depressed. Then it goes immediately to 10 degrees out. Since i swapped everything and the fault did not move to bank 2 there should be no issue with the sprockets or timing. That leaves me with the cam sensor. Attached is the graph at startup.
I will be ordering a new sensor tomorrow.
Any input from the electrickery gurus would be appreciated.

https://drive.google.com/file/d/1TOKOxpFp7LCvX1xlXrsgpywwx0Vq9MWV/view?usp=sharing

New camshaft sensor installed, and the issue still persists. I have checked the wires from the cam sensor to the ecu. No issues there. Cam sensor ground is also good, since it grounds thru the ecu that means the ecu ground is good. At least that one, there are 4 of them that all go to the same ground point I will check the rest as well but i dont expect any issues there.
The "Actual inlet variable valve timing position", is less than 1/2 degree total on the good Rover for both banks. The faulty one reads the same on bank2 but bank 1 is 9+ degrees out. Since the "Intake variable camshaft timing" # are actually changing with engine RPM on both Rovers. This may mean that the "Intake variable camshaft timing" #s are the actual cam sensor readings. And i wonder if the "Actual inlet variable valve timing position" #s are a calculated # using the math of the crankshaft position for a feed back loop verification.
I will take the crankshaft sensor off my good Rover and try it on the faulty one.
Oil pressure not reaching the VVT sol maybe but if the above is true then it is not mechanical. Thats about all i have left before adding some ATF and snake oil to the engine oil in a hail mary hoping that this is the case.

Any thoughts on something i may have missed??? Besides a bullet or a stick of dynamite.
Im at a complete loss here.

I don't know much about cam timing aspects on these particular engines but I'll pass on a few thoughts.

You can usually check cam sensor signals using a cheap oscilloscope.

The ECU normally aims for a particular cam timing because that timing makes most power at the given rpm, which usually means the particular timing traps most charge in the cylinders. Since there are 2 cylinder banks if one bank has less great timing than the other cylinder bank it won't trap as much charge as the good bank. Not trapping as much charge means it won't need as much fuel for mixture to be correct, which can be reflected in fuel trims being more negative on the bad bank and more positive on the good bank because they're both fed from the same MAF and normally both banks flow 50% of the intake air. You could check fuel trims to see if they give any clue one cylinder bank is trapping more charge than the other.

If you've got a blockage in the exhaust, say a blocked cat, it prevents the cylinder bank breathing as well. If it can't pump exhaust out it can't get fresh charge in, so again fuel trims go more negative.

I know of a few engines / ECU's that generate cam timing associated (cam sensor, cam actuator) error codes if the exhaust is blocked or (rarer) if a lambda sensor or knock sensor is failing.

You're seeing readings for cam timing and other readings for actual cam timing. Might expect cam timing to be aimed for cam timing, actual cam timing to be cam timing readings. Similarly the ECU probably sends data via OBD for aimed for mixture (lambda equivalence) and actual mixture.

Lpgc. I hoped you would jump in on this.
I did not think of the fuel trims and cats. I will check them. But since i cant drive it im limited there.

Lpgc wrote:

You're seeing readings for cam timing and other readings for actual cam timing. Might expect cam timing to be aimed for cam timing, actual cam timing to be cam timing readings. Similarly the ECU probably sends data via OBD for aimed for mixture (lambda equivalence) and actual mixture.

Yea I couldnt quite translate my thoughts properly there. The faulty reading is a calculation to verify commanded position vs actual position and something is screwing up that calculation. Unfortunately I cant see/read the commanded position and I dont know how the calculation is derived However from the "actual" readings which im assuming are taken from the camshaft sensor. Since there is no rough running farting or sputtering. And we can see that they are responding the same as bank 2. Which means the mechanical part of the system is working properly and properly timed as well
I did try the crankshaft sensor from my working Rover to no avail.
I will check all the other engine sensors to see if i can find a correlation somewhere.

After reading your post #9 I was under the impression you were seeing command / called for cam timing figures plus also seeing read / actual cam timing figures. After reading your post #11 I'm not so sure what readings you see now, it's probably a good idea to ask you again what readings you see, what field names does your OBD reader term them..?

I think you're saying you believe the 9 degrees reading is a calculated field, command timing minus actual timing (or in other words calculated discrepancy / calculated how much it still needs to adjust cam timing on that cam)? I'm not so sure, usually OBD doesn't show you how much an ECU thinks it has to change things, they usually shows actual readings and some show aimed for readings... E.g. Similarly a vehicle with wide band lambda probes will show actual mixture (lamda equivalence ratio) and will probably show command mixture (command equivalence ratio) but won't show a calculated field for the difference between and actual mixture, it won't show you how much it wants to adjust mixture by to achieve command mixture.

I've re-read the thread and see you've had / have problems with the chains? I wonder if the base timing is correct (if the chain is on the sprocket in the correct position and not say a tooth out)? If the cam sprocket were say a tooth too advanced on the chain the actual timing would be more advanced than it should be (or vice / versa) which could cause the VVT not to have enough range of adjustment to be able to achieve command timing, or at least not within range of the usual PWM it thinks it should give the cam timing mechanism to achieve comman timing. If that were true then you might always see a difference between command timing and actual timing because the VVT doesn't have enough scope for adjustment to achieve command timing.

How many teeth are on the cam sprockets? Maybe we could calculate how many degrees base cam timing would be out if it's sprocket were on the chain one or two teeth out? E.g. If there were 36 teeth on the cam sprocket then a tooth out would mean 10degrees of cam rotation out.

When installing the sprockets and tensioners did you relieve the tension on the tensioners? I skipped through a Youtube video, a guy working on one of these engines used a 'hand grenade pin' to relieve tensioner tension https://www.youtube.com/watch?v=be_O42OoDpE

As i see it
"Intake variable camshaft timing bank 2" and "Intake variable camshaft timing, bank 1" I think are the actual cam position calculation from the crank and cam sensors. Readings fluctuate with engine speed 62.5-61 degrees. They are similar to each other and comparable to the readings of my good Rover Which ironically should mean that they system is actually working as it should

"Variable valve timing bank 2 output duty ratio" and "Variable valve timing bank 1 output duty ratio" is the PWM signal being sent sent to the solenoid actuators.

"Actual inlet variable valve timing position, bank 2" and "Actual inlet variable valve timing position, bank 1" are the result of a feedback error calculation target valve timing angle +- actual camshaft timing = Actual inlet variable valve timing position OR this may also be the timing adjustment command. it seems to be a calculated value for some part of the timing system, not directly reading a cam or crank sensor.

I cleared the codes and then collected this reading.
The latest graph
(https://drive.google.com/file/d/1h7YIBzQ4ozGM-mykPW4ZwvUXHeB8N462/view?usp=drive_link)
For comparison here is the same graph taken from the good Rover
(https://drive.google.com/file/d/1uu8KleuSBdLJXQyMiadj7cq0-FLidDDB/view?usp=drive_link)

As for the chains, I am very familiar with that video, My chains are very similar to his with respect to the tensioner length, So the should be ok, both are equal length and do not appear overly stretched. I have retimed the engine twice with better results each time. Before i opened it up the timing was similar to my good Rover at 60 and 65 degrees. The "grenade pin" comes in the timing kit, however a drill bit of similar size will also work. They are removed before tightening the sprockets and another tool is used to tension the chain and sprockets prior to and during the initial tightening sequence. Since my first attempt did not resolve the issue. I went in again and checked to make sure the sprocket in question was locked in place. Since i found nothing wrong with it I removed the chains and sprockets then reinstalled them on the opposing banks. If the chains or sprockets were at fault this should have resulted in the fault moving to bank 2. Sadly that was not the case. I then replaced the cam sensor with a new one from Rover hoping for a result as i dont own a scope. I took the crank sensor from my good rover and tried that as well. No luck However i did notice a change in the exhaust smell with that sensor and it went away after putting the original one back in.

To summarize Im certain this is not mechanical. The engine runs too smooth for a cam to be that far out of sync and/or from a faulty sprocket. A sensor can create a 0 input and the associated jump. I dont think its possible for a mechanical fault to cause a reading like that without sound or vibration evidence. This leaves me with another sensor that is faulty and should correlate with the jump. Or the ecu is faulty. Unfortunately swapping the ecu out is not an option,
Its times like this I really miss carburetors.

i can understand your comment about carburetors, and your frustration with fuel injection, but i can tell you that today's fuels doesn't run very well with carbies , and todays fuel injection systems are to complicated for their our good. this is because of the push for more enviro-friendly cars. if your cars were tuned for power and economy, their would-be huge increase in power and economy, around 20% in fact, and they tell you its for your benefit, i think its a waste of fuel and money and makes cars over priced and getting worse.
when you fit fuel injection on to a type 1 VW engine you can see the benefits (60-year-old motor) but when you are trying to fix modern day injection systems it's frustrating to say the least. easy to see why people just walk away from them. but what's life without a little challenge.

Carbies didn't always run that well in the old days either. But at least they ran, And yes fuel injection is a step up in economy, power and to some extent reliability. But we also give up a lot of simplicity that meant you could still use your vehicle when it wasn't quite right. And we could come up with more than one creative way of finding issues. Sometimes the solution was simply to turn the radio up louder. We didnt have have to deal with warnings and buzzers constantly flashing in you face while driving And most importantly a substantial failure didnt generally result in unscheduled engine disassembly. That usually required stupidity.
As for the VW i had a 73 Beetle. I had to pull the motor and change the transmission. That took all of 4 hours single handed, from park the car to drive it away. The hardest part was jacking the car up high enough to pull the engine out from under the bumper skirt.
Im still up for the challenge thats why in on here, but at 61 years old the mind is writing cheques that the body cant cash. My days of coming home from work and pulling an engine before bedtime are over. Thats now been relegated to weekends.