I hear you Sean and Datsport, that's why the car will go to the indy for a boost test and second opinion.

But how do you check clogged cats?
And should the downstream sensor not be all over the place?

 

Today had the Indy doing a test ride, they are pretty convinced it is not exhaust or cat related, and further pretty surprised about the "good" readings on the OBD2 and the otherwise smooth ride.

We then decided to take off the S/C cover, indeed not that much work.

Moving the rotors by hand, or on the pulley, there are 3 noises:
1. The coupler is surely toast, and it rocks forward and backward,
2. The rotors itself are contacting each other quite heavily. The noise in the video is purely the rotor contact, not the coupler,
3. I think I hear some bearing noises.

Their conclusion is that this S/C is toast as it is now.
The valve seem to work ok, and nothing feels or sounds loose, but I will probably buy a new actuator, maybe a new valve.

Here is the video:

https://www.youtube.com/watch?v=jaIF...ature=youtu.be

And here some pictures of the damage to the rotors:

 

i beg to disagree about the rotors contacting . that would sound much worse .
and would look much worse also .
and your lobes look fine .

you can hear the broken coupler, and hear some wear in the strait cut rotor gears
emulating through the hollow rotor blades .

hold one rotor still wile you wiggle the other one lightly you will see what i mean .


contacting/striking rotors look like this

 

Oh Jezz, what did I do to get involved in this job?

Frankly, now I don't know any more ...

I let the guys get to their own conclusions, without telling them my own thoughts, so I was happy with their conclusions for a couple hours.... now I am back at square one.

We gave the car a full check top and bottom (on the lift), front to rear.
It is not using oil, there is hardly any oil in the intake, compression is good, no bypass, the cats sound solid, the fuel presure is ok for the full range, both pumps work, sensors are where they should be, no excesive trims, etc etc ...

I really have no clue what else can eat some 60hp away.

It might sound stubborn, but my guts still tell me it is S/C related, valve, rotors, efficiency, leaks, seals, whatever, probably a combination.

But your reply, which I regard very valuable, makes I don't know any more what to do next.
I don't dare to buy parts, but I also don't know what to check next.

Maybe I should just go to sleep ....

 

I saw something recently non Jaguar related, an AMG was low on power turned out to be the intercooler pump failed and the ECM inhibited the engine by retarding the ignition. No engine light but 380bhp down to 320bhp - on a cobra dyno.
Could you hear the IC pump when you turned the ignition on? I'd guess Jaguar have a similar ECM failsafe, might have a look at the wiring diagrams later on.
Having driven with a knock sensor off I know how the car feels, a knock sensor fault and the ECM retards the ignition in the same way the pump might, but the pump will not give a code like the knock sensor....
Also, the SC only really needs the snout rebuild kit...

 

I actually kept an eye on the spark advance gauge (as per Torque Pro) from the beginning, as a UK friend on this forum had a long trial of lacking power and shift delays, finally to be the knock sensors (not giving a code!).

The gauge goes all the way from ~4 degrees way up at full load.
But I failed so far to find the maximum advance value it should be in the literature.

On the pump, it is running, at least by the noise of it.
It is a very distinctive 'extra' noise over my N/A car sound.

On the SC, so what you both say is that the base should be fine, right, just need a rebuild?
There is surely metal to metal contact between the rotors on the front, hard to see on the pic, but the metal shines though and is scratched.
It that excessive bearing play you talk about?

 

it doesn't look bad to me .
you will have to remove the blower regardless to swap the coupler out .
once the snout is removed you can literally rock the gears back an forth to check the gear mesh .
and at the same time you can lift the gears to check for bearing play .
its very un unsual to see the front bearings go bad , as they are semi submerged in oil . were as the rear needle bearings just have a dollop of grease to last the life of them . and fail some wot more often .
don't be alarmed when you see the oil come out dark grey or black and smelling
indescribably tearable , thats normal .

you need to pull the upstream o2 sensors out and look in there with a bore scope not for melted cores but for clogged cores .they don't necessarily have to rattle to be spent .
. my moneys on the cats and the coupler .

 

OK, so I have put the whole SC thinking aside for a while, follow your ideas, and am reading through clogged cat cores, and its remedies (if any).

As usual, hard to select the serious info from the bla-bla stuff on Youtube, so what's your opinion on it if I may ask?

Should it not be easier to lift the car, take the cats off and inspect them visually?

Do you think a good spirited and hot drive might still clean things up?

I read so many things about cleaning them, including high pressure hosing, what's your idea?

E.

 

Eric , did you allready did a boost measurement ?

It's super easy to do

 

So the SC is working, albeit with a little play. There are no codes. But there is a lack of power,
Cat blockage as suggested - remove and eyeball the matrix condition on both.

Loss of boost pressure - via leaking seals, difficult to trace unless there are obvious signs of escaping air, outlet duct seals and top plate seal suspects. Along with boost valve and actuator - disconnected actuator rod? can't see from pic or stuck butterfly. Belt slip, condition of pulleys and SC belt. But you would get 'some boost'.....so check boost pressure

Already checked, throttle position - reset initial low %.
OBD show no signs of ECM intervention via retarded ignition.

It's down to blockage after the manifolds, or leaking under the hood - there's your 2 to checks, not the SC as that's within boundaries.

One thing that bugged me was the code pointing to the cam reluctor, if the ECM feels the engine isn't timed it goes into safe perimeter, has the code popped up again at all Eric? Has it skipped? Has it had the tensioners done? Also as it's an AJ26 has it 2 or 4 O2 sensors?

 

I am baffled how you guys can judge a SC from just a pic and a lousy vid, how do I wish one of you was my neighbor ...

Sean, your list is about it, with the following remarks:

- The lack of power is most obvious on the low revs, ~1500rpm.
If you puddle along in traffic, and push the accelerator 'normally', it goes way too slow, if you push the accelerator all the way, it shifts down properly, but still goes like a slow XJ8.

- No history on the spark plugs.

- No indication on oil use or bypass.

- We moved the boost valve mechanism, no obvious noises, full swing, and it snaps back with the spring-load.
I can see the mechanism moving in different positions if I blip the engine.
As there is some boost, i doubt the valve blade 'disappeared'.

- The surroundings around the belt are clean, no residue, but of course belt slip is hard to determine. It seems tight as it should.

- Boost gauge is on order.

- CAM sensor: Yes, it keeps coming back, looks it throws the codes if the engine is really hot, but I am not sure if Torque gives the warning live, or with a delay.
I have never pushed the engine while cold, but I enter a 5% incline almost immediately from my house, and I dare to say the car struggles identical before and after the code.

- I am sure it has not skipped, it should have a whole different idle.
Full tensioner job is on the list.

- Car has 4 O2 sensors (where I think the AJ26 had heated upstream, and normal downstream, right?).
I can not detect abnormalities in the downstream sensors (which I think I have identified in Torque Pro).

It should be interesting to know the maximum value of the spark advance.

E.

 

max advance should be around 30*

 

I spent yesterday afternoon (re)checking some of the points you mentioned.

- The timing advance range is 4.5 ~ 37 degrees after 30km ride with various full accelerations.

- The S/C pump is working, and I feel flow through the hoses coming from it.

- I measure a maximum boost of 17.8 in/HG on my Torque Pro (still waiting the permanent gauge).
Seems this is the boost, but is it not high?

- If full acceleration & kick-down, the boost built is steep, but drops off immediately after reaching top.

- Boost seems not consistent on full acc, sometimes just 8, sometimes higher, one time the 17.8. Belt??

- Whatever the pressure, it is slow ...also according third person driving XJR.

- Not checked the Cats yet, waiting for a thermometer first.

 

And a typical boost development graph:

 

judging by the max advance , there is no chance this car is in limp mode .

also if the iat2 is set up the same as the later 4.2 cars . then you can not take boost readings from obd . only the vacuum will be accurate .
plus it should not be boosting past 12.5psi on the 4.0 SC .

so ill say it again , you need to look at the cat converters . if something is holding it back .
is there a pinging sound under full throttle ?
this was my cats at 170000km.


choked up for sure .
it made an astonishing power difference when i fitted these .

 

Thanks (again) Andy!

As mentioned before, we are a bit more limited on taking parts off and leave the car for weeks in the service place.

Anyway, based upon all info from you guys, plus our own observations we have made up the plan.

We will rebuilt the existing S/C with new bearings, coupler, oil, etc. as it sounds horrible.
I ordered the kit for new clamps, seals, and the likes for the S/C, to be sure on boost leakage.
We will renew all tensioners, chains etc at the same time.
We will replace several other parts like thermostat, hoses, belts, and all the other things easier to do with the S/C off.
We will visual check the Cats while the car is on the lift.
I ordered a high temperature thermometer gun and the boost valve, so we can perfectly check 'before' and 'after'.

Drove the car back to its storage 400km south, it again performed perfectly as a N/A ... and the codes for the sensors never came back ....

Thanks for all the help on this thread, it is highly appreciated.
To be continued in some weeks I guess.

 

Keep us posted !

I can't wait to hear what the issue is , i'm having the same symptoms and did not find the source yet

 

Yeah, I hate unfinished threads, so will get back to you.
Just might take a bit ...

E.

 

So the car is in for the service.

- The SC was checked on boost, seems it made 12psi, and is now on the bench for a rebuild.

- The Cats were checked with a gauge, and both showed no temperature difference at idle between top and bottom.
A quick look inside one of them with a small mirror showed some contamination, so it become more obvious they are indeed part of the problem, just as suggested here.

- The timing covers are off, and we can see the tensioners were changed (I presume in Japan), but the guides were not (and in pretty bad shape).

However, the mechanic just send me these 2 pics of the left and right bank, with the timing tool installed at the crank.
Obvious, the timing is off by anything between 1/2 to 1 tooth on all 4 cams, and I was just wondering what you guys think what effect this should have on the power problem we had.

 

Are these photos with the engine locked as per the W/s manual? Or at TDC? They look out of place by quite a bit.