S1 V6 auto back on the road at last!! - Problem solved!!

The place to show off and tell us all about your XMs (or even other cars). Should it be a big project, or just some general pics, start your thread in here.
Post Reply
sdelasal
Has changed a sphere or two
Posts: 288
Joined: Thu Aug 19, 2010 11:05 pm
Location: Chelmsford, Essex.

Re: S1 V6 auto back on the road at last!! - fourth time luck

Post by sdelasal » Wed Feb 22, 2017 12:05 am

John, matthew, I'd suggest the following. Assuming a 0-5v range, and assuming that below 10% and above 90% are for diagnosing open circuit and closed circuit faults, then that gives a workable range of 0.5 to 4.5V. So closed throttle should be one of those values, depending on what way the sensor works with respect to the throttle. WOT should then be the other value. 3.8V is somwhere in the middle and not right for closed throttle. These voltages can be checked with engine off, ignition on.
Last edited by sdelasal on Wed Feb 22, 2017 7:13 am, edited 1 time in total.

xantia_v6
Could do a 2.1 headgasket
Posts: 1382
Joined: Sun Mar 31, 2013 5:09 pm
Location: Christchurch, New Zealand or Beaune, France

Re: S1 V6 auto back on the road at last!! - fourth time luck

Post by xantia_v6 » Wed Feb 22, 2017 6:09 am

Some of the current symptoms are certainly puzzling.

One thing that might have been misinterpreted earlier is the split in the manifold sensor hose. An air leak hear will cause the sensor to see less vacuum and the ECU will add more fuel and the engine will run rich, not lean.

If the engine has run consistently rich for some time, the catalytic converter can have overheated, and could now be partially blocked.
1999 XM Exclusive V6 24V ES9 Manual (LHD) 105,000 km
1997 Xantia Exclusive V6 (RHD) 45,000 miles

xmexclusive
Global Moderator
Posts: 5633
Joined: Wed Apr 15, 2009 8:11 am

Re: S1 V6 auto back on the road at last!! - fourth time luck

Post by xmexclusive » Wed Feb 22, 2017 10:41 am

When the Lexia arrives it may be worth making reference checks on another V6.
I have mentioned ECU limp mode a few times so it may be worth giving examples:
Component malfunction - Butterfly position.
Values measured - outside tolerances.
Back up values used - Single fixed value used with minor adjustment for accelerator released or fully depressed.
Warning lamp - on.
So in this state visual position of the butterfly is no indication of ECU instruction to the engine.
I think that butterfly position has been used as a part of the fault finding analysis.
Component malfunction - Mixture richness.
Outside tolerances - Fixed value used.
Warning lamp on.

So it is effectively that the ECU has a "do its own thing" engine protection mode.
In that situation what will the Lexia read?
Not found an answer to that, I suspect it could be values read, the alternative is values used by the ECU.

Note that the Fenix 3B is unusual in that any glitch in the 12 volt feeds or earths to the ECU wipe all stored fault codes as does battery disconnection.
If the keypad immobiliser is fitted Citroen require it reset to 0000 (isolated) before any maintenance work is attempted.
This is to avoid inadvertent immobiliser lock out caused by component disturbance.

There is also the note about wrong wiring of oxygen sensors.
This can destroy them so correcting the wiring does not then repair the sensors.

John

User avatar
MTXM
Citroen God!
Posts: 4862
Joined: Mon Apr 20, 2009 8:45 pm
Location: Aylsham Norfolk

Re: S1 V6 auto back on the road at last!! - fourth time luck

Post by MTXM » Wed Feb 22, 2017 10:43 am

Reading this makes me so grateful for my dull, boring, lethargic but reliable 2.0 Si!!!
The 2.0i is a nice motor Rob that also an ecu and all the same sensors to boot, so I do not think it is a specifically V6 problem! Regards, Matthew T.
1989 V6 Exclusive (Poland car)
1990 V6sei auto (grey auto)
1990 V6sei manual (gold car)
1990 V6.24 Pallas (Germany car)
1990 V6.24v (Scotland car)
Other previous XM sold and broken too many to mention!

User avatar
MTXM
Citroen God!
Posts: 4862
Joined: Mon Apr 20, 2009 8:45 pm
Location: Aylsham Norfolk

Re: S1 V6 auto back on the road at last!! - fourth time luck

Post by MTXM » Wed Feb 22, 2017 10:53 am

The spec is 0-5v linear over 0-6500rpm
Thank you for that John and just a brief update initially to confirm that I checked the throttle sensor with a meter and the range is 0.85-2.85v approx., which I think is acceptable and that might suggest the Lexia is fibbing!

I am also not convinced about there being an issue with the oxygen sensor, since after unplugging and substituting for a known good sensor fitted loose there was no change. The removal of the sensor also brought up the appropriate fault code.

In response to Mike I had expected a inlet manifold leak that apparently does cause a lean mix and then found the split pressure sensor pipe, which if resulting in a rich mix may have been the cause of the high oxygen sensor readings possibly? The disconnection was extremely brief so I think the cat will be fine.

With regards,

Matthew T.
1989 V6 Exclusive (Poland car)
1990 V6sei auto (grey auto)
1990 V6sei manual (gold car)
1990 V6.24 Pallas (Germany car)
1990 V6.24v (Scotland car)
Other previous XM sold and broken too many to mention!

User avatar
MTXM
Citroen God!
Posts: 4862
Joined: Mon Apr 20, 2009 8:45 pm
Location: Aylsham Norfolk

Re: S1 V6 auto back on the road at last!! - fourth time luck

Post by MTXM » Wed Feb 22, 2017 10:58 am

When the Lexia arrives it may be worth making reference checks on another V6.
I also thought that would a good idea John and I have at least two trouble free cars on which I can run checks!
With regards,
Matthew T.
1989 V6 Exclusive (Poland car)
1990 V6sei auto (grey auto)
1990 V6sei manual (gold car)
1990 V6.24 Pallas (Germany car)
1990 V6.24v (Scotland car)
Other previous XM sold and broken too many to mention!

User avatar
Dean
Global Moderator
Posts: 6012
Joined: Wed Apr 15, 2009 7:53 am
Location: Isle of wight

Re: S1 V6 auto back on the road at last!! - fourth time luck

Post by Dean » Wed Feb 22, 2017 11:01 am

You are right Matthew but with the 2.0i I find the fault finding process a lot easier on a wet and windy day if I can take a coffee and sit in front of the engine, usually on the front cross member and if the weather gets too foul, close the bonnet over myself, it makes life a little easier and more comfortable, I would have to be considerably slimmer to do the same with a V6, probably with weird alien like triple jointed fingers and arms.

D
92 Citroen XM Prestige 3.0i Auto R.P5678
14 Mitsubishi L200 Trojan
89 Talbot Express motorhome Auto-Trail coachbuilt (looking for bonnet, wings, scuttle panels etc)

Addicted to Crackanory

xmexclusive
Global Moderator
Posts: 5633
Joined: Wed Apr 15, 2009 8:11 am

Re: S1 V6 auto back on the road at last!! - fourth time luck

Post by xmexclusive » Wed Feb 22, 2017 11:03 am

Hi Matthew

According to the manual anything less than 4.5 volts on full throttle puts the ECU into limp mode.

John

User avatar
MTXM
Citroen God!
Posts: 4862
Joined: Mon Apr 20, 2009 8:45 pm
Location: Aylsham Norfolk

Re: S1 V6 auto back on the road at last!! - fourth time luck

Post by MTXM » Wed Feb 22, 2017 12:17 pm

That is very interesting John and it certainly does feel like limp mode! I have just tried two other sensors and none will read above 3.3v, even when removed from the throttle, so what could cause the volt drop, other than a bad connection including an earth? The wires have continuity to the ecu and the ecu itself also appears to be good. With regards, Matthew T.
1989 V6 Exclusive (Poland car)
1990 V6sei auto (grey auto)
1990 V6sei manual (gold car)
1990 V6.24 Pallas (Germany car)
1990 V6.24v (Scotland car)
Other previous XM sold and broken too many to mention!

User avatar
MTXM
Citroen God!
Posts: 4862
Joined: Mon Apr 20, 2009 8:45 pm
Location: Aylsham Norfolk

Re: S1 V6 auto back on the road at last!! - fourth time luck

Post by MTXM » Wed Feb 22, 2017 12:35 pm

I also meant to mention that I did this check following your earlier post John and the readings I obtained were around 4.85v and 0.8v, so not far off being correct. Regards, Matthew T.
You do not have the required permissions to view the files attached to this post.
1989 V6 Exclusive (Poland car)
1990 V6sei auto (grey auto)
1990 V6sei manual (gold car)
1990 V6.24 Pallas (Germany car)
1990 V6.24v (Scotland car)
Other previous XM sold and broken too many to mention!

Post Reply