Citroen XM Forum

xantia_v6 wrote:I know from experience with V12 Jaguars that air-flow balance between the banks is critical to getting the engine running properly. A trick I use on those is to rig up a manometer made from a piece of clear plastic tubing with one end connected to the manifold on each bank to check that the vacuum is balanced at all engine speeds.

Thanks for that, but in this case it doesn't apply as there is a single manifold serving all six cylinders, whereas the Jag used two manifolds and carburettors.

What is strange is that it will run fine for a while, then start to die off, then come back again. The only code of relevance is the '63' for the rear Lambda sensor.

Dean wrote:
Looking good though.

D

Which is why after a look around it to ensure it wasn't fully rotten, the owner kept saying XYZ doesn't work and I just said..."Not worried about that".

The Lambda issue is a bit annoying as it means I can't move forward onto other things...or maybe I can...

It's amazing how much fluid can dissapear into the spheres. 7 x 400+cc = 2.8+ litres.

Dean wrote:Ah of course, 2 Lambda sensors to control both banks independently, duh!

I was wrong with which bank had the sooty sensor, the front bank is the black one...even more confusing.

The ACAV valves operate in unison, but are in the open state as default.

"What is strange is that it will run fine for a while, then start to die off, then come back again."
- Does it behave any differently if you disconnect both of the new oxygen sensors?
- Do you have access to a lexia? I assume not!
- does the engine have independant high pressure injectors rails, one per bank, or is it a single unit?

On the front outrigger rust, will you be repairing that yourself? Every car i've seen has had rot in that area! In one case the steel had just disolved under the very solid underseal!

Memories of a Gunson's 'Carbalancer', Mike. I still have one in the workshop. Used to be able to tune twin SUs blindfolded!

White Exec wrote:Memories of a Gunson's 'Carbalancer', Mike. I still have one in the workshop. Used to be able to tune twin SUs blindfolded!

A tube in your ear works better.

I once had a Vauxhall slant engine with a cracked valve seat. You could hear hte different induction sound.

sdelasal wrote:"What is strange is that it will run fine for a while, then start to die off, then come back again."
- Does it behave any differently if you disconnect both of the new oxygen sensors?
- Do you have access to a lexia? I assume not!
- does the engine have independant high pressure injectors rails, one per bank, or is it a single unit?

On the front outrigger rust, will you be repairing that yourself? Every car i've seen has had rot in that area! In one case the steel had just disolved under the very solid underseal!

Two linked fuel rails.
No apparent difference with sensors disconnected.
No Lexia, but I can use a DMM.

It is possible that what it needs is a good thrashing, but no legalities make that difficult.

I will do the rust repairs. They rust at the front wheelhouse section because A: it takes a battering and B: it is double skinned, so any moisture getting in just sits there.

One should consider underseal to be sacraficial.

You should probably measure the fuel pressure.

I will, but it starts Ok both hot and cold and also appears rich, rather than lean. The ECU error cose is relating to teh Lambda sensor not being seen.

It also does something rather strange with the fuel guage. Sometimes the guage will go all the way to full andthe warning lamp will flash. Not sure what that means.

The ECU uses an internal set of values if either lambda sensor is not seen or value out of range.
Fault on either Lambda sensor is classed as Minor.
Fault on Lambda sensor heating is classed as Serious.
None of these faults operate the engine warning lamp.

John