My Citroen XM 3.0 PR-Vestige

[xmexclusive]

As I stated in the posts on MTXM's problems the engine warning light is a 3 stage system.
For minor faults the ECU will hold on for 5 seconds at start up to indicate presence of fault.
It will then apply correction strategies to run dealing with the minor fault(s) as programmed.
For poor, out of spec or missing data the ECU substitutes an acceptable figure drawn from its memory.
This can be very confusing when fault finding and why recorded faults may appear to be a mistake.

It may help to show how the flywheel sensor data is processed.
Ignition system schematic (XM 1 no 1 p 22).

V6deanFsen002.jpg

Engine ECU interfaces (XM 1 no 1 p 15).

V6deanFsen003.jpg

Flywheel sensor processing diagram (XM 1 no 1 p 16).

V6deanFsen001.jpg

ECU operation (XM 1 no 1 p 26).

V6deanFsen004.jpg

John

[White Exec]

A great deal elaborated in those pages, John.
Not least importance of gap tolerances between flywheel (crank) sensor and perforated plate - even if 'not adjustable'.
Also details how the tacho (and ignition) is fed too.
Illuminating.

[MTXM]

I was sorry to hear of your continuing woes Dean and in relation to the running and fault codes I would advise carefully checking the ecu circuit board for any damage or mods and especially if the engine has been run on gas. The noise is a mystery and especially as it comes and goes and seemingly does not relate to engine speed. Is the sound more internal than external and can you narrow down the location and character, ie. engine or gearbox, mechanical or hydraulic? Regards, Matthew T.

[Dean]

Thank you John, very helpful as always, I will study that when I get home.

The extent of my investigation into the noise was captured on video in the youtube link a page or so back, if I put my head by the gearbox the noise sounded like it was coming from the bell housing, if I put my head by the alternator it sounded like it was coming from the crank pulley, if I put my ear by the hydraulic pump it sounded like the valve gear, it just seams to come from everywhere.

I had the ECU apart a while back and there is no sign of fiddling, burnt contacts or tracks or modification, the ecu looks fine and for now I don't suspect any problem there, YOG ran on gas fine and I think the only reason it wouldn't run on petrol is the seized fuel pump and dead injectors.

I have now received the coolant pipe so I plan on fitting that tonight and running the engine again properly to see if my TPS sensor wiring problem I found has cured the problem, the engine seemed very happy until it started to warm slightly and a TPS working in reverse must have an awful effect on the engine.

While the noise is of some considerable concern I am trying to look on the bright side and am hoping for an external solution to the problem! by external I mean outside of the block or timing cover, in fact i'm struggling to think what would make that noise, pistons, cam bearings, crank journals and mains all have been ruled out in my head, it sounds like a rubber noise or worst case a fluid noise, I do hope its not an oil pressure relief valve issue, im sick of the sight of the inside of that timing cover already!!!!

D

[Dean]

When Mr XantiaV6 said the speed sensor and crank sensor are different things a while back (I was listening, honest) I wonder if he is on to something. The wiring diagrams show the speed sensor as being the crank sensor (I have made bigger mistakes in this project lets be honest) and did not show a road speed sensing device but I will recheck that as the diagram above clearly shows road speed monitored by the engine ECU but the inline sensor of the speedo cable is connected only for the Hydractive, I wonder if I'm missing a coms wire between the Hydractive ECU and engine ECU somewhere or I've not looked at the wiring diagram properly.............

Mind you disconnecting the crank sensor doesn't bring any other faults up..............

D

[MTXM]

On my Lexia checks for the suspension the 'speed sensor' is mentioned Dean that I agree is not the same thing as the engine speed sensor, crank sensor or flywheel position sensor. I can also confirm that my engine will not run with the crank sensor disconnected, which seems reasonable I guess given the vital data provided! From the details provided by John I note the vehicle speed sensor does feed information to the engine ecu. Regards, Matthew T.

[MTXM]

In relation to the noise I remember the difficulty that I had in pinning down the rattle of my failing engine-t/c flex plate Dean, so I do sympathize. Hopefully in your case it is something minor and accessible and not behind the timing cover as you suggest! Regards, Matthew T.

[Dean]

My Rad hose turned up this morning right on time! so after rushing home from work and doing the bed time story i played.
The noise was evident this evening for a short while after startup but slowly died away completely and did not return after 3 or 4 minutes running, the smoke poured out of the engine bay as i think one of the exhaust headers had oil in its heat shielding and of course the high temp paint had to bake on, plus oily residue on everything.
The engine runs so much better but did have the odd slightly wooly moment when cold, reving between 1500-2500rpm produces the most horrific vibration in the cabin but i think thats because none of the exhaust rubbers are on and its just resting on blocks under the car initial application of the throttle does still cause a stumble and rough running but the situation did improve the longer it ran, still think there could be work to do there though.
https://youtu.be/kehcselI2Zg" onclick="window.open(this.href);return false;
There was a scary moment when i cought sight of a web full of water in the V but then remembered i spilt it there.............Phew!
But then removing the oil cap found a fair bit of mayo, cleaned it and after 5 minutes it went all white again, then after leaving a couple of minutes found this
IMG_0226 by Deanxm, on Flickr
Im crossing my fingers and praying its just damp from an engine thats been siting about assembled but unused for a few months and a few short start ups while running badly

Ready for a test drive around the block soon! if it will run ok..............

D

[MTXM]

That is better news Dean and I would not be too worried about a little moisture on the oil filler cap as all my V6 do this after standing! Regards, Matthew T.

[Dean]

That is comforting Matthew thank you!

D