KE-Jetronic Lambda control (duty cycle check & adjustment)
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I wish I had known this before the plug in my FD tower was taken out in order to adjust the screw to get the regulated emission level measurements passed...
Oh well, that was over eight years and > 100 000 km ago, fortunately I still do have a great running M103 (which is well past the 500 000 km mark).
I look forward to gathering all the info here and checking the parameters someday soon, thank you so much H.D. for all the training provided.
MfG,
Seppo
Oh well, that was over eight years and > 100 000 km ago, fortunately I still do have a great running M103 (which is well past the 500 000 km mark).
I look forward to gathering all the info here and checking the parameters someday soon, thank you so much H.D. for all the training provided.
MfG,
Seppo
I‘m planing to make a PDF manual about the KE-Jetronic‘s Lambda control after I will have added a number of further things about this topic here in this thread. That PDF manual will contain everything I said & still will say in this thread in an edited form plus explaining diagrams, time permitting.
I‘d like to make other CIS-E related PDF manuals too … for instance about (partly little-known) CIS-E tests & interpretation of the results, which can take a lot of guess work out of troubleshooting and lead to targeted diagnosis. … But that is a significantly wider topic than "Lambda control" and definitely takes more time than I will have anytime soon.
I regard understanding Lambda control as such an important basis for targeted troubleshooting on CIS-E engines, that I wanted to talk in detail about this topic first. ...
If the duty cycle (or the EHA current) was not checked before that plug was taken out and the adjustment screw was turned and it is unknown exactly how far in which direction it was turned ... then it is impossible to tell what caused the engine not to pass that test before the adjustment screw was touched. … As I said in my last post, in that case unfortunately “diagnostic information is gone for good“.
Assuming that the adjustment was done solely based on exhaust gas measurement at the tail pipe instead of based on EHA current or duty cycle, I‘d check at least the latter.
Thank you for appreciating this thread.
H.D.
Joined
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I know, we talked about it a while back. My offer still stands, I can save you a lot of of time formatting and publishing it when you're done and ready to post it here.
Thank you very much, GreenT. .. I remember your offer and I‘d like to take you up on it if necessary.
It‘ll take some time anyway until I will have added several other things to this thread first. These are things that are, IMO, important to know in order to understand this least understood function of the KE-Jetronic that “Lambda control“ is with its function chain “o2 sensor → CIS-ECU → EHA → FD“, and what the commonly misunderstood “duty cycle“ is trying to tell us and how we should react on that. … I hope that, so far, particularly posts 39 & 40 are helpful for some readers in that regard. …
H.D.
BTW, I recommend owners of CIS-E cars without that plug in the Lambda adjustment tower to plug it somehow !
An unplugged Lambda adjustment tower is a vacuum leak that allows unmetered air to go into the engine. … When you plug it, do that in such a way that the spring-loaded adjustment pin in the adjustment tower is not push down ! … I use self-made wooden plugs for that.
H.D.
An unplugged Lambda adjustment tower is a vacuum leak that allows unmetered air to go into the engine. … When you plug it, do that in such a way that the spring-loaded adjustment pin in the adjustment tower is not push down ! … I use self-made wooden plugs for that.
H.D.
Member luckymike asked me to explain how Lambda control was originally set and whether it is possible to set it back to the correct setting after the Lambda adjustment screw has been tinkered with.
Consider that the “duty cycle adjustment“ is actually, as I said, an adjustment of the EHA‘s operating range … and that, when that adjustment was originally done, everything was new & clean & (supposed to be) well working. Under these conditions the Lambda adjustment screw was set to the position at which the EHA current fluctuated around zero milliamp (EHA baffle plate fluctuating around its currentless rest position), which is represented by a duty cycle fluctuating around 50%.
Contrary to common belief, that adjustment was done irrespectively of o2 sensor voltage and exhaust emissions. The EHA current (fluctuating around zero milliamp) was the only parameter for the adjustment. …
Exhaust emissions were checked after the adjustment was done.
If they were according to specification, everything was fine … and the Lambda adjustment tower was sealed with a (difficult to remove) plug.
If they were not according to specification, there was either a fuel combustion affecting problem (not necessarily with the injection system) or a problem with the o2 sensor or with the CAT or an exhaust leak between cylinder head & CAT. … In such a (very rare) case the exhaust emissions were, of course, not corrected by turning the Lambda adjustment screw but by fixing the problem that caused the emissions to be out of spec while the EHA current was fluctuating around zero milliamp (duty cycle fluctuating around 50%).
Conversely, the duty cycle indicates, according to its purpose, whether there is/are (a) fuel combustion or Lambda control affecting problem(s) or not … which after ~30 years is often the case, of course.
If you know that the Lambda adjustment screw has never been tinkered with, or exactly how far it has been turned in what direction in relation to its original setting, or what the duty cycle reading was each time before & after the Lambda adjustment screw was touched, then the duty cycle can still be used as a reliable basis for diagnoses … which, depending on its value/range, points to or excludes specific potential problems. After fixing all problems, if any, the EHA current, respectively the duty cycle, not only can but should be readjust according to the procedures in post 2.
If you do not know whether the Lambda adjustment screw has been turned or how far it has been turned in what direction, then, as I said in post 40, “valuable diagnostic information is gone for good (!) and everything that has an effect on fuel combustion (see examples under “Please note“ in post #2) has to be checked first before further touching the adjustment screw, in order to reliably restore a proper condition of the system“ !
It may sound like a broken record, but this post should further help to realize that the Lambda duty cycle is a provider of diagnostic information … and not something that should be ignored or simply readjusted via Lambda adjustment screw. I continuously see the latter being suggested here at BW instead of first checking/fixing all potential problems that can cause the duty cycle reading to deviate from the above mentioned setting range. The duty cycle should primarily be readjusted by fixing the problem(s) that cause(s) its deviation !
This post should also help to understand that using the o2 sensor voltage or exhaust emissions as parameters for adjustments via adjustment tower (instead of the EHA current, or at least the duty cycle) is a bad idea ! … It may get the car through an emission test, but shorten the engine‘s life !
H.D.
Consider that the “duty cycle adjustment“ is actually, as I said, an adjustment of the EHA‘s operating range … and that, when that adjustment was originally done, everything was new & clean & (supposed to be) well working. Under these conditions the Lambda adjustment screw was set to the position at which the EHA current fluctuated around zero milliamp (EHA baffle plate fluctuating around its currentless rest position), which is represented by a duty cycle fluctuating around 50%.
Contrary to common belief, that adjustment was done irrespectively of o2 sensor voltage and exhaust emissions. The EHA current (fluctuating around zero milliamp) was the only parameter for the adjustment. …
Exhaust emissions were checked after the adjustment was done.
If they were according to specification, everything was fine … and the Lambda adjustment tower was sealed with a (difficult to remove
) plug.If they were not according to specification, there was either a fuel combustion affecting problem (not necessarily with the injection system
) or a problem with the o2 sensor or with the CAT or an exhaust leak between cylinder head & CAT. … In such a (very rare) case the exhaust emissions were, of course, not corrected by turning the Lambda adjustment screw but by fixing the problem that caused the emissions to be out of spec while the EHA current was fluctuating around zero milliamp (duty cycle fluctuating around 50%). Conversely, the duty cycle indicates, according to its purpose, whether there is/are (a) fuel combustion or Lambda control affecting problem(s) or not … which after ~30 years is often the case, of course.
If you know that the Lambda adjustment screw has never been tinkered with, or exactly how far it has been turned in what direction in relation to its original setting, or what the duty cycle reading was each time before & after the Lambda adjustment screw was touched, then the duty cycle can still be used as a reliable basis for diagnoses … which, depending on its value/range, points to or excludes specific potential problems. After fixing all problems, if any, the EHA current, respectively the duty cycle, not only can but should be readjust according to the procedures in post 2.
If you do not know whether the Lambda adjustment screw has been turned or how far it has been turned in what direction, then, as I said in post 40, “valuable diagnostic information is gone for good (!) and everything that has an effect on fuel combustion (see examples under “Please note“ in post #2) has to be checked first before further touching the adjustment screw, in order to reliably restore a proper condition of the system“ !
It may sound like a broken record, but this post should further help to realize that the Lambda duty cycle is a provider of diagnostic information … and not something that should be ignored or simply readjusted via Lambda adjustment screw. I continuously see the latter being suggested here at BW instead of first checking/fixing all potential problems that can cause the duty cycle reading to deviate from the above mentioned setting range. The duty cycle should primarily be readjusted by fixing the problem(s) that cause(s) its deviation !
This post should also help to understand that using the o2 sensor voltage or exhaust emissions as parameters for adjustments via adjustment tower (instead of the EHA current, or at least the duty cycle) is a bad idea ! … It may get the car through an emission test, but shorten the engine‘s life !
H.D.
Again, thank you H.D. for your detailed & most knowledgeable contribution(s) here.
Last year I was about to take my 500SEC to a dyno and have them reset the CO readings as my car now has tri-ys, cat delete front pipe, and the Remus rear section..
I got reading your words and quickly realized that unsealing the Lambda adjust was a bad idea... As the car idles, runs smoothly, & performs enthusiastically, I'll leave it alone at this point.
MBL
Last year I was about to take my 500SEC to a dyno and have them reset the CO readings as my car now has tri-ys, cat delete front pipe, and the Remus rear section..
I got reading your words and quickly realized that unsealing the Lambda adjust was a bad idea... As the car idles, runs smoothly, & performs enthusiastically, I'll leave it alone at this point.
MBL
Thank you very much for your appreciation MBL.
The Lambda adjustment tower not being sealed anymore is not a big problem … it can easily be plugged (see post 48). … Blindly tinkering or rashly readjusting the duty cycle (respectively EHA current) with it are bad ideas. Only those readjustments are advisable that are done after all specific potential problems that caused the deviation have been checked and, if necessary, fixed.
Lambda control and exhaust gas emissions are two different things. … Lambda control is based on feedback from the (hopefully healthy) o2 sensor which knows nothing about exhaust gas emissions, except for residual oxygen. Thus Lambda control is only based on the amount of residual oxygen in the exhaust gas … which depends not only on the air/fuel mixture, btw. :wink_2: … Depending on possible fuel combustion affecting problems Lambda control may still be able to keep the amount of residual oxygen, that‘s reported by the o2 sensor in the form of voltage, within spec … of course, with effect on EHA current & duty cycle, possibly also on exhaust gas emissions. Once the exhaust gas has passed the o2 sensor, the only thing that still has an effect on its emissions is the CAT (as far as it‘s still existing, respectively working).
That is why (after fixing all possible fuel combustion affecting problems !) the Lambda adjustment tower should only be used to adjust Lambda control, not exhaust gas emissions. If after the adjustment according to EHA current (respectively duty cycle) the exhaust gas emissions are within spec, congratulations! But don‘t try to keep the exhaust gas emissions within spec via Lambda adjustment tower, if that results in an EHA current fluctuation range far from zero milliamps, respectively in a duty cycle fluctuation range far from 50% !
H.D.
The Lambda adjustment tower not being sealed anymore is not a big problem … it can easily be plugged (see post 48).
… Blindly tinkering or rashly readjusting the duty cycle (respectively EHA current) with it are bad ideas. Only those readjustments are advisable that are done after all specific potential problems that caused the deviation have been checked and, if necessary, fixed.Lambda control and exhaust gas emissions are two different things. … Lambda control is based on feedback from the (hopefully healthy) o2 sensor which knows nothing about exhaust gas emissions, except for residual oxygen. Thus Lambda control is only based on the amount of residual oxygen in the exhaust gas … which depends not only on the air/fuel mixture, btw. :wink_2: … Depending on possible fuel combustion affecting problems Lambda control may still be able to keep the amount of residual oxygen, that‘s reported by the o2 sensor in the form of voltage, within spec … of course, with effect on EHA current & duty cycle, possibly also on exhaust gas emissions. Once the exhaust gas has passed the o2 sensor, the only thing that still has an effect on its emissions is the CAT (as far as it‘s still existing, respectively working).
That is why (after fixing all possible fuel combustion affecting problems !) the Lambda adjustment tower should only be used to adjust Lambda control, not exhaust gas emissions. If after the adjustment according to EHA current (respectively duty cycle) the exhaust gas emissions are within spec, congratulations! But don‘t try to keep the exhaust gas emissions within spec via Lambda adjustment tower, if that results in an EHA current fluctuation range far from zero milliamps, respectively in a duty cycle fluctuation range far from 50% !
H.D.
I remember my CI fuel injection training at Volvo Service School during the early-mid 1970s.
I believe it was the leading edge of fuel injection technology at the time. I think we got the oxygen sensor in '76. We pulled the OX. sensor out of the front pipe, inserting the CO machine probe upstream of the catalyst and used the 3mm Allen to achieve 1.0% CO.. [as I remember]. Back in the day, it worked very well.
Our MB W126 injection is far more exacting, isn't it? Many more considerations to take into account, before any additional action is taken.
M.
I believe it was the leading edge of fuel injection technology at the time. I think we got the oxygen sensor in '76. We pulled the OX. sensor out of the front pipe, inserting the CO machine probe upstream of the catalyst and used the 3mm Allen to achieve 1.0% CO.. [as I remember]. Back in the day, it worked very well.
Our MB W126 injection is far more exacting, isn't it? Many more considerations to take into account, before any additional action is taken.
M.
Absolutely! … The K-Jetronic (CIS) and the KE-Jetronic (CIS-E) are two very different animals, not only regarding the Electronic part … so different that I started this whole thread (under “Basics“) by pointing to one of the (significant) differences between them. …
Your technical expertise and input HD is hugely appreciated!!! and we are talking on a global scale here
One thing that is another curve ball is the Euro high output non catalyst KE-Jetronic M117 engines do not have an O2 sensor - so it takes all the lambda setting with duty cycle measurement out of the equation as no way of measuring O2 level
I am not sure how the MB mechanics back in the day were trained to fine tune these engines, but i would assume they simply used a gas probe in the exhaust pipe?
I have recently purchased an Innovative LM2 digital wideband air/fuel ratio meter and am going to go dual wideband O2 sensors (for left and right side down-pipes) to get a more accurate reading for fine tuning.
Plus huge added advantage of data logging when your out and about driving on roads in varying engine load conditions which is really important info
https://www.innovatemotorsports.com/products/lm1.php
I think that is the only way to go about doing it with today's smart technology at a reasonable cost for DIY tuning versus taking the car to a dyno tuner who still has to have a very good understanding of the Bosch Injection system - which we know very little do.
The added advantage of the LM2 meter is it can be used on any car engine, so once you have tuned your M117 the O2 sensor can be removed and the bung plug screwed in to seal off the opening.
Would be very interested in your feedback on the Euro High output engines and how they went about tuning those engines back in the day?
One thing that is another curve ball is the Euro high output non catalyst KE-Jetronic M117 engines do not have an O2 sensor - so it takes all the lambda setting with duty cycle measurement out of the equation as no way of measuring O2 level
I am not sure how the MB mechanics back in the day were trained to fine tune these engines, but i would assume they simply used a gas probe in the exhaust pipe?
I have recently purchased an Innovative LM2 digital wideband air/fuel ratio meter and am going to go dual wideband O2 sensors (for left and right side down-pipes) to get a more accurate reading for fine tuning.
Plus huge added advantage of data logging when your out and about driving on roads in varying engine load conditions which is really important info
https://www.innovatemotorsports.com/products/lm1.php
I think that is the only way to go about doing it with today's smart technology at a reasonable cost for DIY tuning versus taking the car to a dyno tuner who still has to have a very good understanding of the Bosch Injection system - which we know very little do.
The added advantage of the LM2 meter is it can be used on any car engine, so once you have tuned your M117 the O2 sensor can be removed and the bung plug screwed in to seal off the opening.
Would be very interested in your feedback on the Euro High output engines and how they went about tuning those engines back in the day?
Thanks a lot for your appreciation KRH.
In post 51 I said:
“… the Lambda adjustment tower should only be used to adjust Lambda control, not exhaust gas emissions. If after the adjustment according to EHA current (respectively duty cycle) the exhaust gas emissions are within spec, congratulations! But don‘t try to keep the exhaust gas emissions within spec via Lambda adjustment tower, if that results in an EHA current fluctuation range far from zero milliamps, respectively in a duty cycle fluctuation range far from 50% !“
The same goes for wideband a/f ratio meters:
If after the adjustment according to EHA current (respectively duty cycle) the meter shows/confirms that the a/f ratio is stoichiometric, congratulations! But don‘t try to keep the a/f ratio stoichiometric (or fuel-consumption-optimized, or torque-optimized) via Lambda adjustment tower, if that results in an EHA current fluctuation range far from zero milliamps, respectively in a duty cycle fluctuation range far from 50% !
The small “wink”-smileywink_2 in post 51 looms larger than it may seem. It emphasizes a very little known, yet very important, fact regarding Lambda control in general, not only in case of CIS-E. There I said:
“Lambda control is only based on the amount of residual oxygen in the exhaust gas … which depends not only on the air/fuel mixture, btw. :wink_2: … Depending on possible fuel combustion affecting problems Lambda control may still be able to keep the amount of residual oxygen, that‘s reported by the o2 sensor in the form of voltage, within spec … of course, with effect on EHA current & duty cycle, ...”
That is why the adjustment (besides only “after fixing all possible fuel combustion affecting problems“ !) should be done solely according to EHA current (or at least duty cycle). This way the engine is protected from damage that can otherwise be inflicted on it during phases where Lambda control is not active (like, for instance, during each warm-up phase). Depending on how far away from zero milliamp the fluctuating EHA current deviates, let alone if it exceeds its leaning / enriching limit, damage can be inlicted on the engine during all running conditions !
Btw, KRH, your post reminds me to member Stutz’s suggestion to add wideband o2 sensor & wideband a/f ratio meter related info (similar to what I had posted in a thread of his about a year ago) to this Lambda control thread. I’ll try to take time for that later, maybe tomorrow.
H.D.
Correct.
Yes, that’s how they did it.
You can use a wideband o2 sensor / a/f ratio meter to monitor Lambda (during driving or in the workshop), if you like. But, on CIS-E cars equipped with o2 sensor (Lambda control), I suggest to do the adjustment neither according to o2 sensor voltage (standard or wideband) nor according to a wideband a/f ratio meter’s reading, no matter how advanced it’s technology is !
In post 51 I said:
“… the Lambda adjustment tower should only be used to adjust Lambda control, not exhaust gas emissions. If after the adjustment according to EHA current (respectively duty cycle) the exhaust gas emissions are within spec, congratulations! But don‘t try to keep the exhaust gas emissions within spec via Lambda adjustment tower, if that results in an EHA current fluctuation range far from zero milliamps, respectively in a duty cycle fluctuation range far from 50% !“
The same goes for wideband a/f ratio meters:
If after the adjustment according to EHA current (respectively duty cycle) the meter shows/confirms that the a/f ratio is stoichiometric, congratulations! But don‘t try to keep the a/f ratio stoichiometric (or fuel-consumption-optimized, or torque-optimized) via Lambda adjustment tower, if that results in an EHA current fluctuation range far from zero milliamps, respectively in a duty cycle fluctuation range far from 50% !
The small “wink”-smiley
wink_2 in post 51 looms larger than it may seem. It emphasizes a very little known, yet very important, fact regarding Lambda control in general, not only in case of CIS-E. There I said:“Lambda control is only based on the amount of residual oxygen in the exhaust gas … which depends not only on the air/fuel mixture, btw. :wink_2: … Depending on possible fuel combustion affecting problems Lambda control may still be able to keep the amount of residual oxygen, that‘s reported by the o2 sensor in the form of voltage, within spec … of course, with effect on EHA current & duty cycle, ...”
That is why the adjustment (besides only “after fixing all possible fuel combustion affecting problems“ !) should be done solely according to EHA current (or at least duty cycle). This way the engine is protected from damage that can otherwise be inflicted on it during phases where Lambda control is not active (like, for instance, during each warm-up phase). Depending on how far away from zero milliamp the fluctuating EHA current deviates, let alone if it exceeds its leaning / enriching limit, damage can be inlicted on the engine during all running conditions !
That was done on a dyno including exhaust gas emission measurements.
Btw, KRH, your post reminds me to member Stutz’s suggestion to add wideband o2 sensor & wideband a/f ratio meter related info (similar to what I had posted in a thread of his about a year ago) to this Lambda control thread. I’ll try to take time for that later, maybe tomorrow.
H.D.
As announced yesterday, here is some more info with regard to “wideband o2 sensors”, respectively “wideband air/fuel ratio meters”.
In case of non-ethanol fuel the “stoichiometric” air/fuel mass ratio (“Lambda (λ) = 1”) is about 14.7 : 1 (14.7 mass units of air to 1 mass unit of fuel). In case of ethanol-containing fuel that ratio is lower. With E10 (10% ethanol), for instance, it is about 14 : 1.
Thus the amount of fuel that the injection system has to mix into the intake air in order to receive feedback from the o2 sensor that is used as representative for “stoichiometric air/fuel mass ratio” or “λ = 1” (450 mV) depends on the kind of fuel. The voltage that the o2 sensor generates depends on the amount of residual oxygen in the exhaust gas, no matter what type of fuel is being used. Voltage above 450 mV represents “λ < 1”, a/f < 14.7 (non-E), respectively < 14 (E10). Voltage below 450 mV represents “λ > 1”, a/f > 14.7, respectively > 14. The (healthy) standard o2 sensor provides voltage fluctuating within a range of about 100 - 800 mV (450 mV +/- 350 mV) which, on an intact sytem, represents a Lambda range of about “λ = 0.98 - 1.02”, respectively an a/f mass ratio range of ~14.4-15 (non-ethanol fuel) or ~13.7-14.3 (E10).
A wideband o2 sensor covers a significantly wider Lambda range than “λ = 0.98 - 1.02” which, however, is irrelevant for the KE-Jetronic. Whenever Lambda control is active the CIS-ECU “wants“ to receive o2 sensor voltage nicely fluctuating (with about +/- 350 mV) around 450 mV which it takes as representative for “λ = 0.98 - 1.02” … and it is designed to control the EHA in such a way that it keeps receiving that, if possible … no matter how much fuel (between enriching and leaning limit) it has to mix into the intake air for that. :wink_2:
If you like, you can additionally check the system (including the standard o2 sensor) with a wideband o2 sensor or a wideband air/fuel ratio meter, of course. … But, if you use a wideband air/fuel ratio meter, unless the type of fuel can be selected on it, don’t let it fool you ! … In case of stoichiometric a/f ratio, the wideband o2 sensor detects "λ = 1", and the meter, ‘assuming’ that you are using non-ethanol fuel, reacts by reading “14.7“. But if you’re using ethanol-containing fuel the actual a/f ratio is lower (14 in case of E10). In order to get the wideband o2 sensor to detect "λ = 1" the mass of injected E10 in relation to the mass of intake air is about 5% bigger than in case of non-ethanol fuel. So, when the meter reads “14.7“ while ethanol containing fuel is being used, don’t interpret that as “a/f ratio = 14.7” … interpret it, independent from the kind of fuel, as “λ = 1” or “stoichiometric“. … :wink_2:
H.D.
In case of non-ethanol fuel the “stoichiometric” air/fuel mass ratio (“Lambda (λ) = 1”) is about 14.7 : 1 (14.7 mass units of air to 1 mass unit of fuel). In case of ethanol-containing fuel that ratio is lower. With E10 (10% ethanol), for instance, it is about 14 : 1.
Thus the amount of fuel that the injection system has to mix into the intake air in order to receive feedback from the o2 sensor that is used as representative for “stoichiometric air/fuel mass ratio” or “λ = 1” (450 mV) depends on the kind of fuel. The voltage that the o2 sensor generates depends on the amount of residual oxygen in the exhaust gas, no matter what type of fuel is being used. Voltage above 450 mV represents “λ < 1”, a/f < 14.7 (non-E), respectively < 14 (E10). Voltage below 450 mV represents “λ > 1”, a/f > 14.7, respectively > 14. The (healthy) standard o2 sensor provides voltage fluctuating within a range of about 100 - 800 mV (450 mV +/- 350 mV) which, on an intact sytem, represents a Lambda range of about “λ = 0.98 - 1.02”, respectively an a/f mass ratio range of ~14.4-15 (non-ethanol fuel) or ~13.7-14.3 (E10).
A wideband o2 sensor covers a significantly wider Lambda range than “λ = 0.98 - 1.02” which, however, is irrelevant for the KE-Jetronic. Whenever Lambda control is active the CIS-ECU “wants“ to receive o2 sensor voltage nicely fluctuating (with about +/- 350 mV) around 450 mV which it takes as representative for “λ = 0.98 - 1.02” … and it is designed to control the EHA in such a way that it keeps receiving that, if possible … no matter how much fuel (between enriching and leaning limit) it has to mix into the intake air for that. :wink_2:
If you like, you can additionally check the system (including the standard o2 sensor) with a wideband o2 sensor or a wideband air/fuel ratio meter, of course. … But, if you use a wideband air/fuel ratio meter, unless the type of fuel can be selected on it, don’t let it fool you ! … In case of stoichiometric a/f ratio, the wideband o2 sensor detects "λ = 1", and the meter, ‘assuming’ that you are using non-ethanol fuel, reacts by reading “14.7“. But if you’re using ethanol-containing fuel the actual a/f ratio is lower (14 in case of E10). In order to get the wideband o2 sensor to detect "λ = 1" the mass of injected E10 in relation to the mass of intake air is about 5% bigger than in case of non-ethanol fuel. So, when the meter reads “14.7“ while ethanol containing fuel is being used, don’t interpret that as “a/f ratio = 14.7” … interpret it, independent from the kind of fuel, as “λ = 1” or “stoichiometric“. … :wink_2:
H.D.
Wow...thanks for your time to wrote that piece. I think you may have solved my problem. 1987 560SL, 72.000 perfectly maintained miles..started stalling at operating temp (80c) after fueling with pure gas (no ethanol). The car was running flawlessly until after that fill up. Starts instantly from a cold start and idles perfectly...then stalls at +/- 80c.. will not restart until completely cold. Is this a duty cycle adjustment candidate?
MANY THANKS...Neil Cooley
MANY THANKS...Neil Cooley
No, that does not make your car a "duty cycle adjustment candidate" … it makes your car a “test & diagnosis candidate“ ! … That‘s what, as I try to convey in this thread, problems generally make cars before they make them “duty cycle adjustment candidates“. … :wink_2:
In your case I suggest to start with pulling off the EHA plug at an engine temperature of about 50-60°C and see if it still stalls at ± 80°C (or higher).
Btw Neil, you may have overlooked post 38 where I said that this thread is meant as a general tutorial about the KE-Jetronic‘s Lambda control and that I‘d appreciate if members start separate threads about their individual issues instead of posting about them in this thread. … Thanks for your understanding in advance.
H.D.
Yes it would be nice to keep this thread clean as a tutorial
So many owners and workshops over the years have blindly tampered with the tower adjustment screw thinking it is like a simple mixture adjustment screw on a carby
One thing you have not covered off is also the EHA hidden adjustment screw
Many online articles in this to go CW on the adjustment to improve idle and performance in the 2000-2500rpm range (cruising speed)
The theory being with the peddle held constant at that range (engine warm) and pressing lightly down on the air-plate plate with your finger the engine should stutter.
If it picks up in revs then it is running too lean and the fix is the EHA adjustment screw is turned CW in increments until engine stutter occurs
Perhaps it is time to talk more about the EHA and temptation to change from the factory setting which is well documented on the various forums
Generally an unidentified vacuum leak or potentiometer with worn tracks can be the underlying source of the problem
So many owners and workshops over the years have blindly tampered with the tower adjustment screw thinking it is like a simple mixture adjustment screw on a carby
One thing you have not covered off is also the EHA hidden adjustment screw
Many online articles in this to go CW on the adjustment to improve idle and performance in the 2000-2500rpm range (cruising speed)
The theory being with the peddle held constant at that range (engine warm) and pressing lightly down on the air-plate plate with your finger the engine should stutter.
If it picks up in revs then it is running too lean and the fix is the EHA adjustment screw is turned CW in increments until engine stutter occurs
Perhaps it is time to talk more about the EHA and temptation to change from the factory setting which is well documented on the various forums
Generally an unidentified vacuum leak or potentiometer with worn tracks can be the underlying source of the problem
Haha … there are many things about the KE-Jetronic I have not talked about yet … which, however, I plan to talk about (in separate threads) when I have more time. But first I‘d like to add several Lambda control related things to this thread.
BTW, I did mention “EHA adjustment“ in this thread (in post 39):
“That is not to be confused (!) with “EHA adjustment” via the small hidden adjustment screw on the backside of the EHA, by which the EHA’s, or to be more specific, its baffle plate’s currentless rest position itself is changed, which is an option that should only be taken into consideration in very few specific cases, verified by specific tests … and carried out properly, again verified by specific tests … and not be discussed in this Lambda control thread, please. :wink_2:“
Let me just say that, properly done, EHA adjustment can at best only compensate other problems that will continue to exist. But only very few of these problems are eligible candidates for EHA adjustment, and all of these few problems are FD related. In all other cases it is much better to fix the problem instead of masking it by changing the EHA adjustment … for the same reason, btw, as it is better to readjust the duty cycle by fixing the problem(s) that cause(s) its deviation instead of via Lambda adjustment screw … namely in order to prevent damage that can otherwise be inflicted on the engine whenever Lambda control is not active !
If, with the engine held constant at 2000-2500 rpm while pressing lightly down on the AFM plate, it picks up in revs, then it is probably (but not necessarily :wink_2
running too lean (in that rev range). Turning the EHA adjustment screw CW can counteract that, of course. But (as with many other EHA adjustment suggestions I‘ve seen online) there are many other things that should be checked in that case first before even thinking about touching the EHA adjustment screw !Btw, I generally suggest to take online info & advice about the KE-Jetronic with a pinch of salt. … It often reminds me to what one of the Bosch engineers who designed the KE-Jetronic once said to me in the 1980‘s. He said that it will be the least understood gasoline injection system, no matter how many will claim to understand it … and that they better hide the EHA adjustment screw … and that a difficult to remove plug in the Lambda adjustment tower is an absolute must. … :wink_2:
H.D.
Some may wonder … and member luckymike specifically asked me … why Bosch/MB enabled future EHA current / duty cycle adjustments using the adjustment tower if it‘s basically better to fix the problem(s) that cause(s) EHA current / duty cycle deviation.
The main reason was the fact that, with a probability bordering on certainty, the adjustment is necessary in case of FD or AFM replacement. … FD refurbishment was not an intended option. Up from a certain, relatively superficial, diagnostic stage Bosch/MB workshop mechanics were/are ordered not to test & diagnose further, but to replace the complete FD and/or the complete AFM assembly … although more detailed tests / diagnoses (that are not described in the FSM) can be done.
Another reason has to do with part replacements in general. Manufacturing tolerances of replacement parts can have an effect on the EHA‘s operation range, thus on the EHA current‘s, respectively duty cycle‘s fluctuation range which, in that case, can & should be readjusted via adjustment tower. … However, consider that, besides manufacturing tolerances, replacement parts can be faulty, which can cause EHA current / duty cycle deviation that should not be readjusted via adjustment tower, of course.
Again … adjustments via adjustment tower should be done only in order to readjust a deviated EHA operating range according to EHA current / duty cycle … and only if all potential problems that cause the deviation have been checked and, if necessary, fixed or manufacturing tolerances of replacement parts require it !
When I have a little more time, I will post detailed guidance in this thread on how to interpret duty cycle readings and how to act on them. …
H.D.
The main reason was the fact that, with a probability bordering on certainty, the adjustment is necessary in case of FD or AFM replacement. … FD refurbishment was not an intended option. Up from a certain, relatively superficial, diagnostic stage Bosch/MB workshop mechanics were/are ordered not to test & diagnose further, but to replace the complete FD and/or the complete AFM assembly … although more detailed tests / diagnoses (that are not described in the FSM) can be done.
Another reason has to do with part replacements in general. Manufacturing tolerances of replacement parts can have an effect on the EHA‘s operation range, thus on the EHA current‘s, respectively duty cycle‘s fluctuation range which, in that case, can & should be readjusted via adjustment tower. … However, consider that, besides manufacturing tolerances, replacement parts can be faulty, which can cause EHA current / duty cycle deviation that should not be readjusted via adjustment tower, of course.
Again … adjustments via adjustment tower should be done only in order to readjust a deviated EHA operating range according to EHA current / duty cycle … and only if all potential problems that cause the deviation have been checked and, if necessary, fixed or manufacturing tolerances of replacement parts require it !
When I have a little more time, I will post detailed guidance in this thread on how to interpret duty cycle readings and how to act on them. …
H.D.
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