Health & Diagnosis of CIS-E engines
I‘d like to point once again to two things that are still frequently reported or, worse, recommended here at BenzWorld:
Fiddling around with the adjustment tower without caring about Duty Cycle or EHA current readings
Readjustment of deviated Duty Cycle (respectively EHA current) readings via the adjustment tower instead of by taking care of the cause(s) of the deviation
The fact that the former is an absolute no-no
should go without saying. But let me illustrate once more what you actually do when you do the latter and why it is a bad idea
to do that, using a metaphor:
Let‘s say you usually wake up at about 7:00 AM. But one day you wake up later. You look at your watch and it reads 8:20. You think that‘s not right, it should read about 7:00. The question what's causing the deviated reading, doesn‘t cross your mind. You just set it back to 7:00. That may make things feel right for you again, but you‘ll be late for work. You‘ll probably not loose your job because of being late once, but if you leave your watch set back to that, in your eyes correct, time reading and don‘t take care of the cause of the deviated reading, namely your oversleeping, there will be consequences.
Translated to the KE-Jetronic, that‘s similar to what you do when you simply readjust a deviated Duty Cycle from fluctuating around say 80% to fluctuating around 50% via adjustment screw without taking care of the cause of the deviated reading, just because that‘s what you think it should read. That may make things feel right for you again, but with Lambda control inactive and the throttle opened, the engine will run too rich now. You will not loose the engine because of too rich mixture during one warm-up phase, but if you leave the Duty Dycle set to 50% and don‘t take care of the cause of its deviation to 80%, like e.g. a vacuum leak
, there will be consequences !
… It would be much better to fix the vacuum leak, instead of masking it by simply readjusting the Duty Cycle via adjustment screw
… If there are no other fuel combustion affecting problems and the adjustment screw has not been messed with, fixing the vacuum leak will automatically make the Duty Cycle fluctuate close to 50% again.
The same applies to simply readjusting a deviated Duty Cycle from fluctuating around say 30% to fluctuating around 50% via adjustment screw. Things may feel right for you again, but the engine will suffer in that case too. If you leave the Duty Cycle set to 50% and don‘t take care of the cause of its deviation to 30%, like e.g. one or several worn injector
(s), the engine will run too rich in the cylinder(s) with the worn injector(s) and too lean in all other cylinders at any engine speed, with & without active Lambda control !
… For the same reason as fixing the above vacuum leak, it would be much better to replace the worn injector(s) instead.
(Note that vacuum leaks or worn injectors are only two of many examples of problems that cause deviated duty cycle readings !
Always readjust a deviated Duty Cycle primarily by fixing what‘s causing its deviation … not by fiddling around with the adjustment tower !
after all potential causes for the deviation have been checked and, if necessary, fixed, the Duty Cycle should be readjusted via Lambda adjustment screw according to the procedures in post #2.
This is not only better for the engine
, but also the only way to maintain the fluctuating Duty Cycle as the (mostly unknown) full-featured provider of reliable & valuable diagnostic information
it‘s supposed to be … (like your watch is supposed to reliably inform you about the time of the day). … It makes troubleshooting a lot quicker & easier. Most DIYers & mechanics think that only a static
Duty Cycle provides diagnostic information (in the form of error codes). But that‘s an error. The fluctuating
Duty Cycle is even a lot more informative … unless the Lambda adjustment screw (and/or the EHA adjustment screw) has been unprofessionally fiddled around with !
Unfortunately, both ^these aspects (the benefit for the engine‘s health and the benefit for diagnosis) are and probably will continue to go mostly unheeded … not only in car forums, but even in “professional“ garages. Fixing problems will probably mostly continue to be tried by guessing & throwing parts at them and by fiddling around with the Lambda (& EHA) adjustment screw(s), regardless of the consequences.
But maybe & hopefully, some readers will give this thread a little more thought and not further neglect the richest and so easy to check diagnostic information that their CIS-E cars constantly provide .. the Duty Cycle .. let alone falsify it by fiddling around with the adjustment tower !
P.S.: Please note what I said at the end of post #38.