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  Topic Review (Newest First)
Today 01:07 AM
Heikkif Ok

But is it so that these engines should not misfire even slightly at any circumstances? Now it only does that before reaching operating temperature. Difficult to say if the difference is closed loop no miss fires and some in open loop. Fuel pressures are within specs and so is duty cycle as far as I understand. Next thing to check is the calibration of measuring flap potentiometer as now I got idle control working.
Yesterday 11:19 PM
H.D.
Quote:
Originally Posted by JR420 View Post
... When you say "plug the Lamda adjustment" I am assuming you are referring to covering the opening that accesses the screw adjustment. If so it will keep debris from entering tube, but it will not do anything to the way the engine operates. ...
It depends on how airtight the adjustment tower is. Pull a hose over it and try to blow air with your mouth through it. If it works, read post 48 of the thread I have mentioned so often in this thread … or forget the air blowing test and generally do what I suggetsed in that post. …

Quote:
Originally Posted by JR420 View Post
... Your issue could be one of many ranging from fuel distributor, fuel injectors, ignition system, vacuum leaks etc. Before touching lambda adjustment (which would be last on my list) I would want to eliminate all potential issues that could be causing the problem. ...
^This is very well said, JR420. …

Quote:
Originally Posted by JR420 View Post
... One thing I have learned is that if someone takes the adjustment route to get a car to pass emissions and makes knowing or unknowing of the consequences it can be very difficult to restore it to factory settings AND you will still have the underlying issues just covered with a not very good band aid. ...
^This is also very well said. …

I‘d just like to add the following words (in blue):
“… it can be very difficult to restore it to factory settings ... or to professionally made settings that were indicated by duty cycle test results after part replacements or fuel type switches (ethanol / non-ethanol) ... AND you will still have the underlying issues just covered with a not very good band aid. …“


Quote:
Originally Posted by Heikkif View Post
... I do not find anything out of spec anymore. It might be that fuel distributor has been rebuilt or replaced since lamda adjustment has been unplugged. Passes leak down test. Previous owner had been playing with adjustments in order to get the car running without any luck. ...
In a case where the Lambda adjustment screw has been tampered with, or you‘re not sure whether it has been tampered with, I basically recommend the two steps that I recommended in my last post.

step 1:
Check and, if necessary, fix everything that has an effect on fuel combustion … not only the injectors … also, for instance, all the other things I mentioned in this thread.

step 2:
Check and, if necessary, readjust the duty cycle via the Lambda adjustment screw.

If step 1 does not come into question, do at least a (proper) fuel pressure test (SP & LCP). ... If that is okay, continue with step 2.

H.D.
Yesterday 06:18 PM
JR420 Heikkif- When you say "plug the Lamda adjustment" I am assuming you are referring to covering the opening that accesses the screw adjustment. If so it will keep debris from entering tube, but it will not do anything to the way the engine operates. Your issue could be one of many ranging from fuel distributor, fuel injectors, ignition system, vacuum leaks etc. Before touching lambda adjustment (which would be last on my list) I would want to eliminate all potential issues that could be causing the problem.

One thing I have learned is that if someone takes the adjustment route to get a car to pass emissions and makes knowing or unknowing of the consequences it can be very difficult to restore it to factory settings AND you will still have the underlying issues just covered with a not very good band aid. Hope that helps, but that is where I would start my journey if I were you.


Quote:
Originally Posted by Heikkif View Post
Hi,

My 1990 420 missfires slightly after cold start at first traffic lights before engine has reached operating temperature. When warm it idles as smooth as possible. Starts as easy as possible too warm and cold. Is that normal or should I suspect injectors or something else?
I do not find anything out of spec anymore. It might be that fuel distributor has been rebuilt or replaced since lamda adjustment has been unplugged. Passes leak down test. Previous owner had been playing with adjustments in order to get the car running without any luck. Ignition coil was defect. Should I plug the lamda adjustment?
Yesterday 08:04 AM
Heikkif Hi,

My 1990 420 missfires slightly after cold start at first traffic lights before engine has reached operating temperature. When warm it idles as smooth as possible. Starts as easy as possible too warm and cold. Is that normal or should I suspect injectors or something else?
I do not find anything out of spec anymore. It might be that fuel distributor has been rebuilt or replaced since lamda adjustment has been unplugged. Passes leak down test. Previous owner had been playing with adjustments in order to get the car running without any luck. Ignition coil was defect. Should I plug the lamda adjustment?
07-21-2019 03:58 AM
lesguy While she appears to be running very well now, H.D. I do plan to check my duty cycle and fuel pressures soon, as a starting point. I’m pretty positive there’s no chance I got lucky enough to nail the adjustments just by touch/feel using no gauges/no proper process/proper tools
07-20-2019 11:09 PM
H.D. @JR420 & lesguy:

As I said, without knowing if the Lambda adjustment screw and/or EHA adjustment screw have/has been unprofessionally tampered with before, everything that has an effect on fuel combustion has to be checked before further touching the adjustment screw in order to reliably restore a proper condition of the system.

That, of course, does not mean that you should otherwise not further touch the adjustment screw. On the contrary, now that both of you know for sure that the adjustment screw has been tampered with (you did it yourself), you should at least check and, if necessary, readjust the duty cycle via the Lambda adjustment screw in order to help Lambda control to do the best it can do under the given circumstances.
However, without first checking everything that has an effect on fuel combustion or at least being sure that there are no further fuel combustion affecting problems, you‘ll never really know whether the system is in proper condition or not, no matter how well it subjectively perceived works.

I do recommend both of you to do at least a proper fuel pressure test (SP & LCP) though before you readjust the duty cycle (!) … in order to get more insight into (not only) both of your EHA‘s. …


Quote:
Originally Posted by JR420 View Post
... I have looked for videos and also posts on adjusting duty cycle. I haven't found yet anything other then using a multi meter that measures duty cycle on the diagnostic ports. Could it be that easy?
You‘ll find out (in detail) by reading post 2 of the Lambda control thread I‘ve mentioned several times in this thread. …

H.D.
07-20-2019 09:31 AM
lesguy Wanted to update this thread with pics of my plugs condition after about 350 (300 highway) miles after install of rebuilt distributor, new Bosch injectors, and tinkering with the EHA adjustment and tower Allen screw. Also adjusted gap to .040 for each, as a test to see if larger gap smoothens idle a bit more. New Lemforder motor mounts go in on Monday evening if no rain
07-20-2019 08:07 AM
JR420 Thanks, I have looked for videos and also posts on adjusting duty cycle. I haven't found yet anything other then using a multi meter that measures duty cycle on the diagnostic ports. Could it be that easy?
07-20-2019 04:17 AM
H.D.
Quote:
Originally Posted by JR420 View Post
... Am I understanding correctly in that diagnostic will never be accurate issue if both have been tampered with ...
Yes … also if only one of them has been tampered with.

Quote:
Originally Posted by JR420 View Post
... meaning in order to correctly adjust I would need to start with a new EHA? ...
If the EHA has been tampered with and you really want to do it right … yes ... unless you know how to properly check the EHA‘s calibration (volume flow !) and, if necessary, how to readjust it to its original calibration.

That, BTW, is not explained in the video in post 53. … (See what I said about EHA adjustment in https://www.benzworld.org/forums/w12...e-driving.html) …

Quote:
Originally Posted by JR420 View Post
... feel confident there are no other ignition or fuel related issues ...
If you are sure that there are no more fuel combustion affecting issues, you should check and, if necessary (as very likely), readjust the duty cycle, respectively the EHA current.

Just don‘t overlook any issues, like fuel pressure problems or a leaky CSV, or vacuum leaks, or problems with the o2 sensor & other sensor input to the ECU, the ECU‘s Lambda control function, the EHA‘s electrical resistance, tiny dirt particles in the FD (which can easily get into it during reinstalation … you might be surprised about the effect a ≥ 0.3 mm particle can have), …
And let‘s hope that the FD was not only properly cleaned & refurbished, but also its calibration was correctly checked and, if necessary, readjusted after refurbishment. You might at least want to check for equal volume flow through each injector pipe port.

H.D.

P.S.: The man in the video in post 55 seems to have been taken in by one of the common misconceptions about the KE-Jetronic. He thinks that, with the difference between SP & LCP being above spec, his engine will run richer. That is not the case, at least not with the engine running at operating temperature, unless Lambda control is not working or the Lambda leaning limit is exceeded (duty cycle = 0%) … which, needless to say, should be prevented, of course. …
07-20-2019 02:18 AM
Heikkif Another video:


On his channel there is a lot of material on KE-jet.
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