M103 Rough idle and vacuum leak - Page 5 - Mercedes-Benz Forum
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post #41 of 176 (permalink) Old 08-25-2017, 10:41 AM
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I tried all these tests and they've all been passed, except for centering the plate ...
Very good … sounds like the AFM and the CP have flawless movability.

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Originally Posted by codycool55 View Post
... Is there a trick to this test, or are circular feeler gauges (at .5 mm) an option? ...
Probably your feeler gauge doesn‘t taper at its end, right? … Instead of a feeler gauge, you can also use something else, like a needle … or a real good eye .

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... since completing the o2 sensor tests my check engine light has come on. I pulled the code and got 5 blinks. If the chart I'm reading is correct this indicates a fault with the o2 sensor.
I hope you did the o2 sensor voltage tests correctly … especially with the very different and implausible readings you reported in posts #34 and #36 I wonder how you measured that. You did not, for instance, connect the wrong part of the o2 sensor connector (the female part that‘s coming from the sensor, instead of the male part) directly to ground with a wire while you did the tests, did you ? … And you reconnected the connector properly, right ?

Besides the movability of the AFM and the CP and the position of the CP, I mentioned three more possible reasons for your problem in post #39 … (based on the o2 sensor voltages you reported in post #38).
And if these values - especially the value of test #4 - are reliable, I add two more suspects:
- the EHA
- and the restrictor in the FD

I‘ll give you further test suggestions after your feedback about my concerns regarding the o2 sensor tests you did.

H.D.
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post #42 of 176 (permalink) Old 08-31-2017, 04:23 PM Thread Starter
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I have not yet tried using another object to measure the gap but I will as soon as I can!

As far as I know I connected the sensor correctly. I did not connect the female plug (coming from the sensor) directly to ground. The results in post 34 were from placing the multi meter directly between the 2 o2 sensor plugs. Yes, the connector is back in place as it was before. I remember a few months ago (6?) The check engine light came on for a day or two but went away before I had the opportunity to check it. Is it possible to reset the light to see if it will come on again?
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post #43 of 176 (permalink) Old 09-01-2017, 06:43 AM
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Regarding the check engine light: since only California cars are equipped with it, which I‘ve never been in touch with, I‘m not sure, but I think the light disappears when the problem that caused it is gone.

Experiences in another forum here at Benzworld lead me to address something general:
So far, I have not suggested to replace any parts or readjust anything to see if the problem goes away … I never do that. I suggest and describe systematic testing, especially in case of the KE-Jetronic. So far we have only done some o2 sensor voltage tests … and there are many more and also more informative tests than those shown in Bosch / MB service manuals / books … which, from Bosch‘s or MB‘s point of view is understandable … they suggest(ed) not to test any further up from a certain test level and to buy and install complete new assemblies, like the FD or AFM …

The tests I suggest here at Benzworld are a lot easier to do than it may seem at the first look at detailed test procedures of mine. Plus, systematic testing helps to understand the system and to avoid unnecessary money spending. … I mention these things, because not everybody cares about understanding the system or saving money. Often people just want to get their cars fixed asap, also at the risk of spending more money … and there is nothing wrong with that.

So, depending on each individual situation, following my advice may not be the most suitable way. But if you are interested, I‘ll post further test suggestions to narrow down the possible causes for your specific problem.

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post #44 of 176 (permalink) Old 09-03-2017, 10:39 PM Thread Starter
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HD, I would love to have the opportunity to learn more about my car, especially if I can save some money in the process. The work done over the past few years on it has really peaked my interest in the automotive industry
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post #45 of 176 (permalink) Old 09-05-2017, 12:38 PM
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I saw your reply by chance, because I did not get any email notification about it. There was a problem with email notifications over many months this year already. … I hope it‘s not back again !?

Okay codycool55 ... since you‘re interested, I‘ll dive a little deeper into systematic testing than I have done so far here at Benzworld. Maybe a few other readers here in the 126 forum will be interested too. I tried to awaken interest in that in another BW forum not long ago, but practically no one there was interested.

The possible culprits I have mentioned so far (based on your information) are:
- fouled / faulty o2 sensor
- incorrect Lambda control adjustment
- incorrect position of the CP lock screw
- incorrect AFM ‘zero position‘ (checked)
- incorrect AFM play (checked)
- sluggish AFM / CP movability (checked)
- contaminated metering slits
- injectors
- EHA
- restrictor

Based on the assumption that especially the o2 sensor voltage #4 you reported in post 38 and the duty cycle of 0% you reported earlier, which do not match with each other, are reliable … the next thing I would do if I had your car here is something I addressed in post 22 of my KE-Jetronic Lambda control thread:
A simultaneous test of:
- fuel pressure (System Pressure and Lower Chamber Pressure)
- EHA current (ampmeter connected in series between EHA and EHA plug)
- o2 sensor voltage (closed loop, voltmeter connected as shown in diagram 1 in post 37)
- duty cycle (terminal 3 at the diagnostic socket)
with the engine at operating temperature, both at idle speed and at ~ 2500 rpm, once with the EHA electrically connected and once with the EHA electrically disconnected.

That sounds more complicated than it is. When I do such a test, I place all (analog) meters next to each other, and since I can not simultaneously watch fluctuating values on several meters, I let my tablet PC, fixed above the meters, record a video of all readings while I carry out the test steps. After the test I watch the video and stop it at interesting moments for detailed analysis.

That test also shows whether the ECU is telling the truth in ‘duty cycle language‘ about what it is telling the EHA in ‘current language‘. Remember, in my Lambda control thread I said that the “fluctuating duty cycle is an easier to check representative of the EHA current, and the duty cycle check / adjustment is actually an EHA current check / adjustment”.

As a side note:
When I check a KE-Jetronic, I always check / adjust the Lambda control directly via EHA current, not (indirectly) via duty cycle. I just quickly compare the duty cycle with the EHA current at the end, only to see if the ECU‘s duty cycle information at the diagnostic socket is reliable. I also never do the “ignition on / engine off“ duty cycle tests I described in my KE-Jetronic Lambda control thread. Neither do I care about static duty cycle error codes when I check a KE-Jetronic. I use other test routines prior to the Lambda control test, that are not described in any service manual, with selfmade test equipment ... covering all of these and many other things more informatively and more reliably.
The duty cycle I only watch occasionally during driving … on the selfmade OBD ‘ashtray‘ I introduced in my Lambda control thread … which is very helpful in tracing (especially intermittent) problems that are represented by static duty cycle values. ... … I might introduce this OBD device a little more detailed here in the 126 forum when I have a little more time.

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post #46 of 176 (permalink) Old 09-09-2017, 09:43 AM Thread Starter
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I have so far still been unable to measure the centering of the AFM plate. I atempted to use the smallest needle I could find but still couldn't fit it in the gap. Just eyeballing it, it does not look off center to me however it does appear to rest slightly higher than the cylindrical portion of the AFM (rests just at the bottom of the tapered part).

If I am only able to come up with one analog voltmeter, which should I use the analog meter on? How can I simultaneously measure system and lower chamber pressures, do I simply need 2 fuel pressure meters? Just to make sure I do this right the first time, would you mind creating a diagram of how to connect the EHA? What range should I be looking for in the voltmeter and ammeter?

Thanks for all the help HD. In regards to your email issue, I'm recieving email notifications so maybe the problem is on your end?

Additionally, my cars performacne and reliability has been sharply declining lately and I fear my spark plugs may need to be changed/ cleaned soon. Will this nullify any of the tests we have done so far?
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post #47 of 176 (permalink) Old 09-10-2017, 11:32 AM
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Your welcome. …

Quote:
Originally Posted by codycool55 View Post
I have so far still been unable to measure the centering of the AFM plate ... ... Just eyeballing it, it does not look off center to me ...
Sounds good enough to me.

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Originally Posted by codycool55 View Post
... however it does appear to rest slightly higher than the cylindrical portion of the AFM (rests just at the bottom of the tapered part) ...
It should be as described under step 5 of the PDF-file I attached in post 39.

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... If I am only able to come up with one analog voltmeter, which should I use the analog meter on? ...
That depends on the meter‘s measuring scale … with 0-1 volt, I‘d use it for the o2 sensor voltage … with 0-20 volts, I‘d use it for the duty cycle (if I had no duty cycle meter). … The meters do not have to be analog, however, with analog meters fluctuating readings are a lot more comfortable to monitor than with digital meters.

Quote:
Originally Posted by codycool55 View Post
... How can I simultaneously measure system and lower chamber pressures, do I simply need 2 fuel pressure meters? ...
Yes. … But if you don‘t have two manometers, one is also okay. In that case measure ‘System Pressure‘ at idle speed and at higher revs first. It should be the same at any rev ! … Then, in the video, measure the much more interesting ‘Lower Chamber Pressure‘.

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... Just to make sure I do this right the first time, would you mind creating a diagram of how to connect the EHA? ...
See attached diagram. … With the key turned to “ignition on“ (engine not running) on a M103 the ammeter should read +20 mA ! … If you see a negative value, change the polarity of the measuring cables !

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... What range should I be looking for in the voltmeter and ammeter? ...
The expected maximum measuring ranges for the described tests on your car are:
- o2 sensor voltage: 0-1 V
- duty cycle: 0-100 %, respectively 0-15 V
- EHA current: 0 +/- 10 mA (+20 mA with ignition on, engine off)
- fuel pressure: 0-5.5 bar (80 psi)

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... In regards to your email issue, I'm recieving email notifications so maybe the problem is on your end? ...
I‘m only receiving notifications about PM‘s, however, with a day or two delay. … In case of new posts in threads I‘m subscribed to, I haven‘t received any notifications for a week now … also not about this post of yours. …

Quote:
Originally Posted by codycool55 View Post
... Additionally, my cars performacne and reliability has been sharply declining lately and I fear my spark plugs may need to be changed/ cleaned soon. Will this nullify any of the tests we have done so far?
As I said in my Lambda control thread, “Generally problems relevant for the fuel combustion have an influence on the EHA control, hence on the duty cycle.”. … And fouled spark plugs, of course, are a problem relevant for the fuel combustion … affecting o2 sensor voltage, thus the ECU‘s reaction (EHA current & duty cycle). … It‘s definitely recommendable to do the tests with good spark plugs !

The closed-loop o2 sensor voltage test (test 1 from post 37) will be part of the simultaneous tests (post 45) … but I also suggest to repeat the open-loop o2 sensor voltage tests (tests 2 - 5 from post 37) with new spark plugs.

And I suggest to complete the simultaneous tests (video) like this:
While the engine is running at idle speed move the AFM plate manually slightly up and down … (a magnet would facilitate moving it up). Keep the plate several times in both positions (the slightly risen one and the slightly pushed down one) for about 2 seconds each. Keep it as far up and down as possible without stalling the engine (which can easily happen!). Do that, like the other simultaneous tests, with the EHA plug connected and with the EHA unplugged.

H.D.
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post #48 of 176 (permalink) Old 09-28-2017, 12:41 PM Thread Starter
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Sorry for the long delay in reply, I've just moved back to college for the quarter and I have been very busy! During the morning prior to moving back I managed to take all the videos. In the past 10 days I forgot which was which, as I forgot to label them... I'm no longer in possession of the meters I used as I had borrowed them from a few people in my hometown. I'm going to attempt to borrow meters from people here but I'm not sure it'll work out. I can post the videos I took but I'm not sure they'll be any use. One thing I did notice that seemed off was my EHA amperage was 25ma with the key off, and with the engine idling was -14 to -15 ma. I also changed my spark plugs and remeasured my o2 voltage but again in my last minute rush to move back to college I misplaced the paper I wrote the voltages on...

I suppose one positive side of this scenario is that in my college town there's a mechanic I have had experience with and seems to know his stuff, and a Mercedes dealership nearby. If I chose to take it to a mechanic or dealership, is there anything specific I should tell them to look for?
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post #49 of 176 (permalink) Old 09-29-2017, 04:11 PM
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Sorry for the long delay in reply, I've just moved back to college for the quarter and I have been very busy ...
Don‘t worry! ... and don‘t feel urged to do these simultaneous tests if that causes inconveniences. I only introduced them because they‘re very informative and help to reduce troubleshooting time significantly … and they‘re part of my basic KE-Jetronic test procedures.

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... my EHA amperage was 25ma with the key off, and with the engine idling was -14 to -15 ma ...
Assuming that you mean “with igniton on, engine off“, I suggest to check the resistance between both EHA pins (should be 18 – 21 Ω).

EHA amperage of -14 to -15 mA with the hot engine running at idle, as well as the 0% duty cycle you reported earlier, point to “too little residual oxygen in the exhaust gas” … provided that all components work well! … Can be caused by a fuel/air mixture that’s rich beyond the system’s leaning limit (in case of M103: -10 mA) for a number of possible reasons (of which wrong Lambda adjustment via adjustment screw is only one) … or by weak / incomplete combustion. … But there could also be a problem with the o2 sensor, falsly reporting “too little residual oxygen in the exhaust gas” … or with the ECU, falsly processing the o2 sensor’s input … or with the EHA, not properly following the ECU’s order … or with the FD, not properly following the EHA’s order … or with the injectors, not properly following the FD’s order, …

… and, especially since the o2 sensor voltages you reported earlier are not in line with this EHA amperage, that’s where the above-mentioned simultaneous tests would come in handy, in order to narrow down this list of possible culprits significantly … possibly down to wrong Lambda adjustment (screw turned to far cw) … or they might point to other suspects, like igniton components. …

The resistance between each pole inside the distributor cap and the respective spark plug connector should be ~ 2 kΩ. The rotor should have ~ 1 kΩ. Between the cap’s center pole and the end of the wire that’s connected to the coil should be < 1 Ω. The coil should have 0.3 - 0.6 Ω between terminal 15 (big hex nut) and terminal 1 (small hex nut), and 8 – 13 kΩ between terminal 1 and the high voltage terminal.

Btw, in your initial post from two years ago you mentioned that you have to depress the gas pedal to start the car. … Is your car equipped with EGR (exhaust gas recirculation)? … If so, make sure there is no EGR related false air involved … might be caused by a stuck open EGR valve, which can not be spray tested.

I assume you made sure that the AFM‘s zero position and play are correct and that the AFM / CP movability is good.

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... there's a mechanic I have had experience with and seems to know his stuff, and a Mercedes dealership nearby. If I chose to take it to a mechanic or dealership, is there anything specific I should tell them to look for?
You might tell them to have a look at this thread. …

H.D.
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post #50 of 176 (permalink) Old 09-30-2017, 03:43 AM
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Good one HD ..
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