Hi
So just to be clear the Lambda sensor does not record a fault code in the ECU if it operates outside normal Parameters?
It can regulate normal idle and fast idle CO HC for MOT purposes but still have a fault.
I just want to be sure as these are the reasons I have not looked at the Lambda, the car has done 110,000 so it could be due.
Can someone give me ballpark price on a new one of these as I guess a second hand one would not be worth trying.
Will it have to be a genuine part etc?
Thanks
Joe
XM V6 Misfire
Moderator: RichardW
The Lambda sensor is a generic type of sensor.
Meaning it is a "basic-method" type of sensor used on all cars. Only the exterior, threading and cable count varies (3 or 4) as may the connector type.
It only works when hot, so testing can only be done while engine is running and then supplying a hot exhaust.
At cold there is no voltage from sensor - and the sensor is simply open circuit if you try an ohmic test.
That's why the build-in heater element to aid a quick working sensor.
The heater element can of course be ohmic checked - and will show a low ohmic resistance 1 - 2 ohms.
It does not have to be a genuine part - which helps a lot on the price tag. They tend to be pricy.
Meaning it is a "basic-method" type of sensor used on all cars. Only the exterior, threading and cable count varies (3 or 4) as may the connector type.
It only works when hot, so testing can only be done while engine is running and then supplying a hot exhaust.
At cold there is no voltage from sensor - and the sensor is simply open circuit if you try an ohmic test.
That's why the build-in heater element to aid a quick working sensor.
The heater element can of course be ohmic checked - and will show a low ohmic resistance 1 - 2 ohms.
It does not have to be a genuine part - which helps a lot on the price tag. They tend to be pricy.
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Stempy
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I was under the impression that the lambda sensor is ignored by the ecu in all cases other than at constant throttle settings, i.e. when steady cruising and at idle, where it works to lean off the mixture to acceptable levels for the cat to be efficient. If you are accellerating and braking the mixture strength is calculated from the various other sensors as the oxygen content will change dramatically under these conditions. Hence the emissions test at the MOT being carries out at a constant 3000 or whatever rpm.
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">I was under the impression that the lambda sensor is ignored by the ecu in all cases other than at constant throttle settings,<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
The ECU uses the averaged output of the lambda sensor to move the whole fuelling map up or down, so it does have an effect at all throttle openings, but for fast changes, this is swamped by rules for extra richness for acceleration etc.
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">it works to lean off the mixture to acceptable levels for the cat to be efficient<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
It depends on your point of view...
The typical failure mode of a lamda sensor (or if you disconnect it) is to make the ECU think the engine is running lean, so it will increase the fuelling, that makes it look like fitting a new lamda sensor causes the mixture to be weakened.
On most engines, the cat/lambda actually works the other way, making the engine richer for the cat to be efficient, as compared to the same engine when the factory did not fit a catalytic convertor.
I have a portable 4 gas analyser that I can use for checking air/fuel ratios while cruising.
On my Jag V12 without cats or lamda, the cruise mixture is about 20:1, that comes down to 15:1 if the ECU is changed and lamda sensors fitted.
The ECU uses the averaged output of the lambda sensor to move the whole fuelling map up or down, so it does have an effect at all throttle openings, but for fast changes, this is swamped by rules for extra richness for acceleration etc.
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">it works to lean off the mixture to acceptable levels for the cat to be efficient<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
It depends on your point of view...
The typical failure mode of a lamda sensor (or if you disconnect it) is to make the ECU think the engine is running lean, so it will increase the fuelling, that makes it look like fitting a new lamda sensor causes the mixture to be weakened.
On most engines, the cat/lambda actually works the other way, making the engine richer for the cat to be efficient, as compared to the same engine when the factory did not fit a catalytic convertor.
I have a portable 4 gas analyser that I can use for checking air/fuel ratios while cruising.
On my Jag V12 without cats or lamda, the cruise mixture is about 20:1, that comes down to 15:1 if the ECU is changed and lamda sensors fitted.
Hi all
I discovered an interesting site to determine EFI parts
http://www.facet.it/index.asp
click on lingua and changein English
then it shows you the way,
Citroen XM estate is there, they say Part Nr.10.7064 and give a nice picture for the connection.
Part Nr.10 7004 is an universal 4 wire type.
So just to be clear the Lambda sensor does not record a fault code in the ECU if it operates outside normal Parameters?
When it is between the 0.1 and 0.9 volts the check engine light doesn't come on.
My cars fuel consumption jumped 50 %upwards during a holyday.The car had 75000 km,was stil driving fast enough but reacted a lot lumpyer in low/mid load regio. I had also lots of white smoke out her exhaust and a chemical smell at exhaust. No lights where coming on. It turned to be a O2 sensor coming to 0.44 volts maximum, The idiots in the garage first told me they had repaired the lambda. After quickly emptying a tank I returned and let thim place a new one.
I taught when you floor the throttle "WOT" at higher RPM the ECU is giving maximum injection, that is the reason I talk about the O2
I discovered an interesting site to determine EFI parts
http://www.facet.it/index.asp
click on lingua and changein English
then it shows you the way,
Citroen XM estate is there, they say Part Nr.10.7064 and give a nice picture for the connection.
Part Nr.10 7004 is an universal 4 wire type.
So just to be clear the Lambda sensor does not record a fault code in the ECU if it operates outside normal Parameters?
When it is between the 0.1 and 0.9 volts the check engine light doesn't come on.
My cars fuel consumption jumped 50 %upwards during a holyday.The car had 75000 km,was stil driving fast enough but reacted a lot lumpyer in low/mid load regio. I had also lots of white smoke out her exhaust and a chemical smell at exhaust. No lights where coming on. It turned to be a O2 sensor coming to 0.44 volts maximum, The idiots in the garage first told me they had repaired the lambda. After quickly emptying a tank I returned and let thim place a new one.
I taught when you floor the throttle "WOT" at higher RPM the ECU is giving maximum injection, that is the reason I talk about the O2
that's the throttle position (stop) sensor, may have some effect, if ecu thinks throttle closed at low butterfly openning, not sure it's the problem.
I've a '89 V6 sei, and it too is a bit rough below 2-3K, perfect when booting it or on a fast run, but low speed seems a bit lumpy. Also had the engine fault light come on a couple times on the motorway at high speed, stayed on for a while then went out again, no codes though?! odd thing was the engine seemed to run smoother after that.
Not had the time to check it all over properly as yet, swapped the ignition module, seemed to improve for a short time then back to same. Like you, seems OK from cold start for a short time, then rough.
regards
Dave
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Joe T</i>
Thanks for this guys its giving me hope,
There is a sensor on the throttle body does that do anything special?
I would have gave up ages ago but I honestly dont know what to replace this with, I had a CX25 DTR Turbo before this and that was a wrench when we finally parted company.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
I've a '89 V6 sei, and it too is a bit rough below 2-3K, perfect when booting it or on a fast run, but low speed seems a bit lumpy. Also had the engine fault light come on a couple times on the motorway at high speed, stayed on for a while then went out again, no codes though?! odd thing was the engine seemed to run smoother after that.
Not had the time to check it all over properly as yet, swapped the ignition module, seemed to improve for a short time then back to same. Like you, seems OK from cold start for a short time, then rough.
regards
Dave
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Joe T</i>
Thanks for this guys its giving me hope,
There is a sensor on the throttle body does that do anything special?
I would have gave up ages ago but I honestly dont know what to replace this with, I had a CX25 DTR Turbo before this and that was a wrench when we finally parted company.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Hi before buy expensive parts buy a bargraph multimeter or borrow one and just measure it http://www.mdaelektronica.nl/webshop.ht ... ml&lang=nl
Dave, I missed your reply whilst off looking for a Lambda.
I have replaced the throttle potentiometer switch which is what I think your referring to, I was told it cant be changed and its set to the throttle body but thats bollo, it just needs a tweak if it doesnt idle or you have a flat spot. Its not like the old throttle switches on BX's from what I can see as it gives a variable reading not an on off type reading.
I was looking at a temp type sensor in the top of the throttle boddy after the butterflies.
I asked about this as whilst trundling through France it started farting about quite bad, I pulled the intake hose off and gave some neat inj cleaner in the air intake, and it responded quite strangely taking a few miles to settle down, then it was fine for about 300 miles.
But if I unplug it I get a fault code so who knows.
I would be up for testing the Lambda but I find it strange that if this sensor starts going mad it does not record a code in the ECU, or even when hot I cant get any codes to come up as its stationary.
Cheers
I have replaced the throttle potentiometer switch which is what I think your referring to, I was told it cant be changed and its set to the throttle body but thats bollo, it just needs a tweak if it doesnt idle or you have a flat spot. Its not like the old throttle switches on BX's from what I can see as it gives a variable reading not an on off type reading.
I was looking at a temp type sensor in the top of the throttle boddy after the butterflies.
I asked about this as whilst trundling through France it started farting about quite bad, I pulled the intake hose off and gave some neat inj cleaner in the air intake, and it responded quite strangely taking a few miles to settle down, then it was fine for about 300 miles.
But if I unplug it I get a fault code so who knows.
I would be up for testing the Lambda but I find it strange that if this sensor starts going mad it does not record a code in the ECU, or even when hot I cant get any codes to come up as its stationary.
Cheers
Hi Joe,
one other thing to check, under the butterfly on the throttle, theres 2 small hoses that connect to the heater pipes (steel ones in the V), and a couple of other hose-type outlets on the body, one of which (or both?) should have a blanking tube present. If it's not there, can give rough idle, stalling, maybe also poor running at low speed?
regards
Dave
one other thing to check, under the butterfly on the throttle, theres 2 small hoses that connect to the heater pipes (steel ones in the V), and a couple of other hose-type outlets on the body, one of which (or both?) should have a blanking tube present. If it's not there, can give rough idle, stalling, maybe also poor running at low speed?
regards
Dave
I will have a look for the pipes, I hope ther easier to find than the lambda sensor. What made me think it would be on the front downpipe? of course not!!
Am I going to need a ramp to change it?
I was only trying to find the connector to confirm the amount of wires? that must come out up the top somewhere?
Cheers
Am I going to need a ramp to change it?
I was only trying to find the connector to confirm the amount of wires? that must come out up the top somewhere?
Cheers
this old post maybe helpfull for you?
http://www.andyspares.com/discussionfor ... IC_ID=6821
Succes,
Willy M.
Belgium
http://www.andyspares.com/discussionfor ... IC_ID=6821
Succes,
Willy M.
Belgium