both driving graphs give the after cat minimum threshold of 0.000v...
Technical Stilo 1.6 LPG idling problem
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Technical Stilo 1.6 LPG idling problem
ivand
New member
Now I am confused; I thought that lambda parameters are used only on steady rpm's, while in any other condition revs (varying) they would be shut off by ECU ??
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if they were shut off during driving how would the ECU know if it was giving the right amount of fuel?
ivand
New member
What I meant to say is that lambdas are shut off during acceleration / deceleration, which corresponds to graph (driving graph).
This also corresponds to provided idle graph, where after-cat lambda is working all of the time.
This also corresponds to provided idle graph, where after-cat lambda is working all of the time.
im sorry ivand i dont really know what your trying to say (i dont mean that in a nasty or aggressive way) lambdas, as far as im aware, shouldnt 'shut off' only send signals to lean out the fuel.
lambdas read oxygen content of the exhaust gases constantly regardless of throttle position/engine speed. this is to report back to the ecu that the correct amount of fuel is being injected. if the mixture 'leans out' on acceleration the lambdas detect more oxygen in the exhaust and send a signal to the ecu. the ecu then ups the fuel delivery until the correct fueling is achieved.
inversely upon deceleration the lambdas would detect less oxygen and send a 'rich' signal to the ecu telling it to dial back the fuel delivery (possibly to the point of injector shut off)
either way the lambdas should only trace between 0.2-0.8v. 0.5v would be the value that the ECU would need to not make any changes to fuel delivery.
FOR EXAMPLE
the pre cat lambda will have large deflections between 0.2-0.8v, cycling every second or so. you would also expect the post cat lambda to be tracing smaller deflections but it err on the 'lean' side to reduce fuel usage.
the latter Idle graphs zoli has provided are what i would consider to be 'healthy' lambda traces ie pre cat cycling between 0.1220v- 0.7910v and post cat requesting a leaner mixture and tracing between 0.6830v-0.7470v
whereas the driving graphs the post cat at times traces at 0.0000v... to me this is the wrong behaviour for any lambda sensor. my suggestion is to change the lambda to see if it helps.
if im honest im worried about the pre cat lambda tracing to 0.0340 but this maybe because the post cat lambda is tracing so low that the pre cat is having to do all the work. the fact that he has P0420 suggests to me that either his cat is broken/damaged/at the end of its life OR his lambdas are on the way out... changing lambdas, as im sure you can appreciate, is by far the cheaper option, especially as they have a limited lifespan anyway.
i may be wrong and if i am thats fine but as i understand it and IMHO lambdas shouldnt trace to 0.0000v at all, ever!
see HERE Q11&Q12
lambdas read oxygen content of the exhaust gases constantly regardless of throttle position/engine speed. this is to report back to the ecu that the correct amount of fuel is being injected. if the mixture 'leans out' on acceleration the lambdas detect more oxygen in the exhaust and send a signal to the ecu. the ecu then ups the fuel delivery until the correct fueling is achieved.
inversely upon deceleration the lambdas would detect less oxygen and send a 'rich' signal to the ecu telling it to dial back the fuel delivery (possibly to the point of injector shut off)
either way the lambdas should only trace between 0.2-0.8v. 0.5v would be the value that the ECU would need to not make any changes to fuel delivery.
FOR EXAMPLE
the pre cat lambda will have large deflections between 0.2-0.8v, cycling every second or so. you would also expect the post cat lambda to be tracing smaller deflections but it err on the 'lean' side to reduce fuel usage.
the latter Idle graphs zoli has provided are what i would consider to be 'healthy' lambda traces ie pre cat cycling between 0.1220v- 0.7910v and post cat requesting a leaner mixture and tracing between 0.6830v-0.7470v
whereas the driving graphs the post cat at times traces at 0.0000v... to me this is the wrong behaviour for any lambda sensor. my suggestion is to change the lambda to see if it helps.
if im honest im worried about the pre cat lambda tracing to 0.0340 but this maybe because the post cat lambda is tracing so low that the pre cat is having to do all the work. the fact that he has P0420 suggests to me that either his cat is broken/damaged/at the end of its life OR his lambdas are on the way out... changing lambdas, as im sure you can appreciate, is by far the cheaper option, especially as they have a limited lifespan anyway.
i may be wrong and if i am thats fine but as i understand it and IMHO lambdas shouldnt trace to 0.0000v at all, ever!
see HERE Q11&Q12
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Lambdas work all The time as Richy has said, if not a car would never fuel correctly, which would lead to premature wear and damage to the CAT.
ivand
New member
I'm so sorry if this looks as arguing, but it is not; I only want to find /confirm the right answer.
This is true about values for pre-cat and after-cat lambda should give from 0.1-0.8 volts.
Also is (what I beleive) true that lambda signals are used by ECU only at steady rpm's.
How ECU calculates amount of fuel is by using informations of various sensors such as TPS, rpm, MAP..., and the lambdas are there to „fine-tune“ fuel so cat can work properly (efficiently).
So, if lambda's are shut-off (or ECU is ignoring their values), the car won't shut down or act un-driveably.
In this case we have good graph on idle both on petrol and LPG. The after-cat is not „grounding“ at all.
What I would do is to make measurements of both lambdas at rpms higher than idle, but at steady rpms.
For example at „steady“ 1500 rpm's, 2500 or any other. Then if graph would show grounding (or 0 V), I would be convinced that something is wrong with after-cat lambda itself.
Once more, if after-cat lambda sensor is bad it would show grounding also on idle graph.
This is true about values for pre-cat and after-cat lambda should give from 0.1-0.8 volts.
Also is (what I beleive) true that lambda signals are used by ECU only at steady rpm's.
How ECU calculates amount of fuel is by using informations of various sensors such as TPS, rpm, MAP..., and the lambdas are there to „fine-tune“ fuel so cat can work properly (efficiently).
So, if lambda's are shut-off (or ECU is ignoring their values), the car won't shut down or act un-driveably.
In this case we have good graph on idle both on petrol and LPG. The after-cat is not „grounding“ at all.
What I would do is to make measurements of both lambdas at rpms higher than idle, but at steady rpms.
For example at „steady“ 1500 rpm's, 2500 or any other. Then if graph would show grounding (or 0 V), I would be convinced that something is wrong with after-cat lambda itself.
Once more, if after-cat lambda sensor is bad it would show grounding also on idle graph.
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zoli
Member
Hi guys, to add to this interesting thread what I know about oxygen sensor function is one also needs to take into account the pre and post cat lambda statuses, are the open or closed loop.
The Pre cat lambda as far as I've seen from the FES is always closed loop (good thing, meaning it's in circuit and if healthy doing it's job) while the after cat lambda is varying, sometimes it's in closed loop sometimes it's not, usually it's in open loop while the car is idling and it's in closed loop mode when the car is accelerating. As far as I understood, and please correct me if I'm wrong, this corresponds to correct behavior because the car and it's ecu can determine according to other sensors values the proper working conditions and it only switches on (closing the loop of the after cat lambda) when needed, similar to what ivan said. The Pre cat lambda is there to make adjustments to the fuel trim while the post cat lambda is essentially checking is the pre cat lambda doing it's job or is the cat it self ok.
Definitely any signal of the lambda sensor should not trace to 0V because that would mean something is wrong, either in the cat or the oxygen sensor it self.
At this point I have not had the cat and the lambdas checked out by my mechanics .... well, because they are "only" mechanics and have limited knowledge in electronics. I took the car to an electronics garage, they hooked it to some kinda professional scanner, took some measurements over a few minutes, took the car for a spin (I was not there I had to leave for work and this is what I'm being told) and finally concluded that they could not find any fault what so ever. I only paid some 10Eur for the check up, no big deal, and I was told all sensors are fine.
I'd honestly like to check just the Catalyst and the Pre and Post Cat lambdas, probably change one of them just to see would it make any difference. The problem in this is that I'd have to order at least one new lambda sensor just to try it out, which at this point I would like not to
but If I'm left with no options I'm going to "throw out" that 80 to 100 Eur for the one lambda sensor just to see would it make any difference. Thou optimally it would be nice just to check it first with a good working lambda and probably by a garage who understand their ways around intake manifolds, sensors, cat's and lambdas (in Fiats, might I add ).
I like that this is turning into quite a nice conversation, I'm learning from it a lot, honestly. This is not by far an argument, but an honest bunch of folks discussing their knowledge and learning from each other.
Thanks for this guys!
The Pre cat lambda as far as I've seen from the FES is always closed loop (good thing, meaning it's in circuit and if healthy doing it's job) while the after cat lambda is varying, sometimes it's in closed loop sometimes it's not, usually it's in open loop while the car is idling and it's in closed loop mode when the car is accelerating. As far as I understood, and please correct me if I'm wrong, this corresponds to correct behavior because the car and it's ecu can determine according to other sensors values the proper working conditions and it only switches on (closing the loop of the after cat lambda) when needed, similar to what ivan said. The Pre cat lambda is there to make adjustments to the fuel trim while the post cat lambda is essentially checking is the pre cat lambda doing it's job or is the cat it self ok.
Definitely any signal of the lambda sensor should not trace to 0V because that would mean something is wrong, either in the cat or the oxygen sensor it self.
At this point I have not had the cat and the lambdas checked out by my mechanics .... well, because they are "only" mechanics and have limited knowledge in electronics. I took the car to an electronics garage, they hooked it to some kinda professional scanner, took some measurements over a few minutes, took the car for a spin (I was not there I had to leave for work and this is what I'm being told) and finally concluded that they could not find any fault what so ever. I only paid some 10Eur for the check up, no big deal, and I was told all sensors are fine.
I'd honestly like to check just the Catalyst and the Pre and Post Cat lambdas, probably change one of them just to see would it make any difference. The problem in this is that I'd have to order at least one new lambda sensor just to try it out, which at this point I would like not to
but If I'm left with no options I'm going to "throw out" that 80 to 100 Eur for the one lambda sensor just to see would it make any difference. Thou optimally it would be nice just to check it first with a good working lambda and probably by a garage who understand their ways around intake manifolds, sensors, cat's and lambdas (in Fiats, might I add ).I like that this is turning into quite a nice conversation, I'm learning from it a lot, honestly. This is not by far an argument, but an honest bunch of folks discussing their knowledge and learning from each other.
Thanks for this guys!
OP
OP
zoli
Member
Hello guys, some further updates on the situation.
I took the time to make 2 more measurements with FES.
1. while idling revving from 700 rpm to 2000ish rpm on PETROL
2. the same while idling but on LPG
Some mighty strange behavioral pattern if you ask me. I'm definitely not the guy to interpret these measurements but if anything they look not normal or even strange to me. As you can see at higher revs the lambda signal act up all strange like, sometimes dipping too low or staying too low or high for several seconds.
I really don't know to interpret this is this behavior OK or not but I'm hoping some of the post readers might.
Z
I took the time to make 2 more measurements with FES.
1. while idling revving from 700 rpm to 2000ish rpm on PETROL
2. the same while idling but on LPG
Some mighty strange behavioral pattern if you ask me. I'm definitely not the guy to interpret these measurements but if anything they look not normal or even strange to me. As you can see at higher revs the lambda signal act up all strange like, sometimes dipping too low or staying too low or high for several seconds.
I really don't know to interpret this is this behavior OK or not but I'm hoping some of the post readers might.
Z
ivand
New member
Well, these new graphs look worse then previously posted (idle) graphs.
It seems that aftercat lambda is acting worse while car is running on LPG.
Looking on „petrol“ graph, I find this interval from 110.1 to 153.3 strange as I beleive it is not supposed to act like that – is lambda cooling off, shutting off or is it just gone bad I cannot confirm but wish to know.
The last part (idle settled) from 165.6 till end of graph signal from aftercat lambda is acting normal (proper) to my opinion.
It seems that aftercat lambda is acting worse while car is running on LPG.
Looking on „petrol“ graph, I find this interval from 110.1 to 153.3 strange as I beleive it is not supposed to act like that – is lambda cooling off, shutting off or is it just gone bad I cannot confirm but wish to know.
The last part (idle settled) from 165.6 till end of graph signal from aftercat lambda is acting normal (proper) to my opinion.
OP
OP
zoli
Member
Exactly. And sadly it does seem more and more that something is wrong around the cat, pre and post lambdas and/or the intake butterfly walve as well. It still can be a lot of things. I really would like to have it fixed...hopefully not for half a fortune
http://ngkntk.co.uk/wp-content/uploads/2011/03/Lambdacat2011.pdfNTK Lambda Catalog said:
that is gospel enough for me! Bosch say pretty much the same thing but trace voltages are acceptable from 0.1v upto 0.9v.
im having difficulty finding any supporting documentation that suggests 0.0v is an 'acceptable' level to recieve from a lambda under any conditions as you have suggested ivand do you have anything available that you could post? im interested to know what conditions i should be considering if i get 0.0v trace on any lambda i may test in the future!
zoli you asked about 'Open Loop' and 'Closed Loop', this is not a representation of the sensors behaviour, merely what the ECU does with the information from the lambdas.
Closed Loop is where the sensor is being actively used by the ECU for idle monitoring and for 'part load conditions' i.e holding a desired engine RPM.
Open Loop is where the ECU disregards the lambdas readings for Accelerating (the ECU will spent much of its time deliberately enriching the mixture to avoid hesitation and to provide extra power) and Decelerating (when most ECU's will shut off the fuel completely to aid economy)
may i appologise for the inaccurate info i posted before (yes, ivan you were correct)
richydraper said:
the reason your status flicks from Open to Closed loop is dependant on what the ECU is doing with the information from the lambdas at that time.
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ivand
New member
Well, I now realize I was wrong thinking that ECU would shut down after-cat sensor in certain area.
There is probably no documentation to find that supports that idea.
Evidently both lambdas are producing some kind of signal all of the time, while ECU decides when to use it for fuel calculations.
I'm so sorry for making confusion. I am still learning and wishing to help.
Thanks Rich for getting it straight.
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OP
OP
zoli
Member
Thanks Richy for the absolute clarifications on lambdas.
I now understand that Open and Closed loop only means that the ECU is taking it into account or not, thou in the back the lambda is still providing a signal (which is what I see from the FES graphs).
Now my task is to have the lambdas checked out, I don't think they were ever taken out, probably they should be inspected at least visually besides measuring their signal with an oscilloscope before.
I read about clogged up cat's as well that can be "simply" taken off and cleaned (well, after some major elbow grease), to improve the drive-ability and the cars responses also fuel economy and hesitation.
How ever I look at it the Intake valve, Catalyst and Pre and Post lambdas have to undergo a check up.
As my finances let it I will do that, probably after Christmas ( my wife would be pissed as hell if I spend money now on the car and not on presents , nor is this what I'd like to do ) . There are several shops, garages and professional mechanics around town, I'll ask around from friends and try to find a good one that do professional electronics and diagnostics.
Still this bugs me so much I want to have it fixed, I like the little Stilo of ours, it's our first ever car yea she's 10 year old but she was taken care of and maybe all is needed is a new lambda (they do break down after a certain mileage)... if anything comes up I'll let you know for sure. Oh oh oh ... Important bit of information, we bought the car with some 98 000 km in it in February 2012, I honestly think the km have been tampered with (the FES even says revwrites 2 times - of course theres no date) and this is what my mechanic said as well, that the car does seem sound and in good condition but he personally thinks it has more than 98k km. We drove in it 13 000 km so far and she never died on us. Just this one more thing with the lambdas and car and I'll be a happy car owner
Z
I now understand that Open and Closed loop only means that the ECU is taking it into account or not, thou in the back the lambda is still providing a signal (which is what I see from the FES graphs).
Now my task is to have the lambdas checked out, I don't think they were ever taken out, probably they should be inspected at least visually besides measuring their signal with an oscilloscope before.
I read about clogged up cat's as well that can be "simply" taken off and cleaned (well, after some major elbow grease), to improve the drive-ability and the cars responses also fuel economy and hesitation.
How ever I look at it the Intake valve, Catalyst and Pre and Post lambdas have to undergo a check up.
As my finances let it I will do that, probably after Christmas ( my wife would be pissed as hell if I spend money now on the car and not on presents
, nor is this what I'd like to do ) . There are several shops, garages and professional mechanics around town, I'll ask around from friends and try to find a good one that do professional electronics and diagnostics.Still this bugs me so much I want to have it fixed, I like the little Stilo of ours, it's our first ever car
yea she's 10 year old but she was taken care of and maybe all is needed is a new lambda (they do break down after a certain mileage)... if anything comes up I'll let you know for sure. Oh oh oh ... Important bit of information, we bought the car with some 98 000 km in it in February 2012, I honestly think the km have been tampered with (the FES even says revwrites 2 times - of course theres no date) and this is what my mechanic said as well, that the car does seem sound and in good condition but he personally thinks it has more than 98k km. We drove in it 13 000 km so far and she never died on us. Just this one more thing with the lambdas and car and I'll be a happy car owner Z
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98,000km is about average for a lambda to fail. I wouldnt worry too much If you cant rig up osciloscopes etc to test. one of the only advantages to doing this is to see the transition time for your sensors ideally it should be between 100-300ms from what i have been led to believe. May i also suggest to you to replace both sensors rather than Just the post cat as this will prevent any future issues... After all this i really hope it is the lambdas and you dont have a blown cat
ivand
New member
Took some time this afternoon playing with MES, and checked aftercat signal on various rpms...it never dropped under 0.097V... Also I've noticed that aftercat seems to be always in open loop until engine reaches about 2000 rpms...
Anyway, here is graph...
Uploaded with ImageShack.us
Anyway, here is graph...
Uploaded with ImageShack.us
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Took some time this afternoon playing with MES, and checked aftercat signal on various rpms...it never dropped under 0.097V... Also I've noticed that aftercat seems to be always in open loop until engine reaches about 2000 rpms...
Anyway, here is graph...
Uploaded with ImageShack.us
least your sensor is good
that makes one out of three!ivand
New member
least your sensor is good
actually, it's two out of three (I put new precat lambda about 4 months ago)
Hi, how did you solve the problem, because I have the same problemThanks Richy for the absolute clarifications on lambdas.
I now understand that Open and Closed loop only means that the ECU is taking it into account or not, thou in the back the lambda is still providing a signal (which is what I see from the FES graphs).
Now my task is to have the lambdas checked out, I don't think they were ever taken out, probably they should be inspected at least visually besides measuring their signal with an oscilloscope before.
I read about clogged up cat's as well that can be "simply" taken off and cleaned (well, after some major elbow grease), to improve the drive-ability and the cars responses also fuel economy and hesitation.
How ever I look at it the Intake valve, Catalyst and Pre and Post lambdas have to undergo a check up.
As my finances let it I will do that, probably after Christmas ( my wife would be pissed as hell if I spend money now on the car and not on presents
Still this bugs me so much I want to have it fixed, I like the little Stilo of ours, it's our first ever car
Z
OP
OP
zoli
Member
Hi reeggis,
To be absolutely honest and to cut a long story short, I did diddly squat about it and the issue went away.
To define it a little bit more, the error or symptom seemed persistens, up to a few weeks, and then it just went away. I cannot really tell when exactly and after how much time but it did bother me for good weeks.
Now the car is idling perfectly...well as perfectly as possible for an 11 year old used ride, but more or less around tickover of 730 - 750 idle rpm.
I still have poor acceleration, at least according to my assumption and the car lacks power is what I feel. This all could be due to anything from a slow lambda through a sticking butterfly valve to a lot of other things... the lack of "umpf" in our Stilo still needs to be looked after but honestly I just keep it in as good a condition as possible until I don't have to take it to the shop again... bad experiences with mechanics
To be absolutely honest and to cut a long story short, I did diddly squat about it and the issue went away.
To define it a little bit more, the error or symptom seemed persistens, up to a few weeks, and then it just went away. I cannot really tell when exactly and after how much time but it did bother me for good weeks.
Now the car is idling perfectly...well as perfectly as possible for an 11 year old used ride, but more or less around tickover of 730 - 750 idle rpm.
I still have poor acceleration, at least according to my assumption and the car lacks power is what I feel. This all could be due to anything from a slow lambda through a sticking butterfly valve to a lot of other things... the lack of "umpf" in our Stilo still needs to be looked after but honestly I just keep it in as good a condition as possible until I don't have to take it to the shop again... bad experiences with mechanics
