Citroen XM Forum

The smoke cleared up, but it appears to be running rich and still has a stumble on opening the throttle.

Today I cleaned the relay contacts and inside ones on the ECU and IGN relays, the others are sealed, then decided to check which cylinders had most/least effect when unplugging the HT lead. This test was a bit andom, but I felt that No-5 was performing least well.

I replaced the HT leads and removed all the spark plugs, which were black...but then the engine was quite cold, so would be runnning a richer mixture.

I interrogated the ECU's to check for fault codes and got an impressive list.

Engine
ABS
Hydractive

All reset after, so I will be able to see which ones return.
The ABS has a particularly good showing of faults, but the light goes out after the self test flashes.



The only two for the engine ECU were rear Bank lambda sensor and Active Intake Valve Long. I have noted the Engien warning lamp is lit, presumably as a result of the Lambda sensor fault.

I connected my meter to read the Lambda output voltage and say 0.2v average, but did fluctuate depending on load, so I believe the sensor is working. The engine was still cold, which may well be the reason for the low lambda voltage.
I noted the engine still stumbles slightly so decided to check the distributor cap and rotor arm.

There were two screws holding the cap on, the lowest one was missing. Of the two remaining, the top was was OK, the front one was corroded so the head couldn't be gripped. I had to resort to removing the battery tray, but still couldn't get the screw to turn with mole grips on the head.
I resorted to arc welding a nut over the head of the screw to get more purchase. This went well until actually undoing the screw...when the head snapped off.



I was now able to remove the distributor cap, but there was a screw shank sticking out of the distributor body. This wouldn't turn when gripped with mole grips and it was looking like I might have to remove the distributor body, cut the screw down and drill it out. This was fraught with danger as the screw is steel, the body aluminium.



Another good go with the stick welder and a new nut again saw the screw shear off, but the heat had made the corrosion break the bond. About 15 minutes work with penetrating oil and mole grips saw the screw out. I then re-tapped all tehree holes...just need new screws now. The cap now has one screw and two twisted wireds holding it on...

Only time I've seen that many fault codes on the abs is with a bad main earth strap, behind n/s headlamp.
O2 sensors usually start working within 30seconds of start.
I've seen rich running, stumble when initially opening the throttle and a hesitation, TPS! Lol
I got an O2 code along with a few others when I first started mine, came back on the first drive but not seen it since though.


D

Think ive got some knackered dizzys with screws in them if that helps. Or you just get some standrd screws localally to go in?

One way or another, I'll get some screws, I'm sure. They are M5 x 30
Regarding the stumbling, I feel it is spark related, but also the rich mixture won't be helping. Very occasionally the Lambda light goes out so things might improve. Bear in mind, the exhaust is ejecting rust when the engine runs, so I suspect the sensor isn't in particularly good condition.

What oil are peeps using in their V6-24?

The manual specifies 15w-50 to give better hot protection. 15w-50 and similar derivatives are now reasonably rare and for larger clearance/performance engines, thus expensive.

I've ordered Total Quartz 7000 10W-50, at a fairly stiff price.

I wonder why you'd use such an expensive oil and 15W-50 at that. Planning to rally in the Sahara? I've always used 10W-40 in both V6 XM I've owned. After Pennzoil I now use Chevron Supreme API SN. The engine runs very well on that and retail is only 600 yen a litre. Change it twice a year, in the spring and in the autumn.

I use 10W-40 for all my cars Will, which is what the Factors always recommend. With regards, Matthew T.

Is 10w-40 the updated recommendation for the PRV 24v as part of the cam gear upgrades though?

D

I can find no mention of change of oil.
Sump was modified early on to incorporate an oil strainer.

John

Due to the risk of valve train drive gear damage due to lack of oil film, I'll stick with the Citroen recommended oil of 50 weight.

In addition, it may be that the 24v engine has greater clearances to promote power output, so will need a thicker oil to keep the bearing gaps.

iirc, the 12v spec is 10w-40.