M103 Rough idle and vacuum leak - Page 10 - Mercedes-Benz Forum
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post #91 of 174 (permalink) Old 12-16-2017, 12:45 PM
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Okay, since your adjustment screw obviously has been messed with (set to extremely lean basic setting) … let‘s try to readjust it. I say “try“ because your EHA is still a suspect … we can test it more specifically later.

First I recommend to carefully read post 2 of this thread:
https://www.benzworld.org/forums/w126...uty-cycle.html
… at least up from “Measuring device“.

Under “Adjustment procedures“ you will read: “... start the engine, let it idle and wait until the reading starts to fluctuate ...”.
In your case it’s unlikely that you will see the duty cycle (voltage) start to fluctuate, because the adjustment screw has been turned way too far ccw. … I guess your mechanic thought that the mixture is too rich and that he should lean it out that way. Would he have done the simultaneous tests you did in post 51 and known how to analyse them, he would have looked at the ignition system components (coil, cap, rotor, leads) first, like you did. …

During the duty cycle test you will probably see a static value of (close to) 100%, respectively (close to) zero volts, with the hot engine idling. In that case turn the adjustment screw cw.

Reagarding the ECU‘s duty cycle output to the round diagnostic socket X11:
As I said, I‘ve never dealt with the California version. But … in addition to what wooky_chew_bacca said in post 56 … considering that the ECU‘s fault code memory needs permanent voltage supply in order to not lose stored fault codes, the ECU is probably automatically switched to duty cycle output to X11 once the ECU connector has been disconnected and reconnected, like it has in your case.

I suggest to measure the depth of the AFM plate at the point where you feel the AFM lever reach the CP … before you touch the adjustment screw … (see attached drawing).

H.D.
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post #92 of 174 (permalink) Old 12-19-2017, 11:55 AM Thread Starter
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Pull off the vacuum line between the throttle valve and the regeneration valve of the fuel evaporation system at the regeneration valve and block it.
What is this referring to?

Just to make sure I'm understanding this right.. [1 - ([Voltage between 2 and 3] / [Voltage between 2 and 6]) *100 gives you your duty cycle. With the engine off but ignition on that should be 85%. Mine should be at 100%. Assuming it is I need to turn the adjustment screw clockwise until the value fluctuates around 47%.

I measured the depth and it was at just about 3/4 inch. I also retook the measurement of play, and it just over 1/8 inch... or about 3-4 mm.. still outside the range of 2mm. Measure twice post once?
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post #93 of 174 (permalink) Old 12-19-2017, 02:51 PM
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What is this referring to? ...
The regeneration valve is what you see within the ellipse in the attached picture. And the vacuum line that comes from the throttle valve is the one the arrow points to. That‘s the plastic tube that has to be pulled off and blocked for the duty cycle test.

Note: The picture shows the engine bay of my 300CE. Your engine bay looks a little different, but the regeneration valve should look the same.

Quote:
Originally Posted by codycool55 View Post
... Just to make sure I'm understanding this right.. [1 - ([Voltage between 2 and 3] / [Voltage between 2 and 6]) *100 gives you your duty cycle. ...
Correct.

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Originally Posted by codycool55 View Post
... With the engine off but ignition on that should be 85%. ...
Correct.

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Originally Posted by codycool55 View Post
... Mine should be at 100%. ...
Well … with the currently reported AFM play (3-4 mm) it may be below 100% … (and increasing the suspicion on the EHA).

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Originally Posted by codycool55 View Post
... Assuming it is I need to turn the adjustment screw clockwise until the value fluctuates around 47%. ...
Yes … turning the adjustment screw cw decreases the duty cycle, and turning it ccw increases the duty cycle.

Respectively … turning the adjustment screw cw increases Vp3 and turning it ccw decreases Vp3.

Example for a measurement with a voltmeter:
If Vp6 is 13.9 V, then the duty cycle is 47% if Vp3 is [1 - (47 / 100)] * 13.9 V = 7.37 V

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post #94 of 174 (permalink) Old 12-20-2017, 02:08 PM Thread Starter
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Something is amiss here.. My engine off duty cycle is 85%, but neither depressing the AFM or the throttle changed the duty cycle. Vp3 while idling is about what vp6 while idling is. This would mean my duty cycle is 0 and therefore I need to turn the adjustment screw counterclockwise.
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post #95 of 174 (permalink) Old 12-21-2017, 11:49 AM
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Originally Posted by codycool55 View Post
... neither depressing the AFM or the throttle changed the duty cycle. Vp3 while idling is about what vp6 while idling is. This would mean my duty cycle is 0 and therefore I need to turn the adjustment screw counterclockwise.
Immer langsam mit den jungen Pferden! (Hold your horses!) … LOL … especially when it‘s about the KE-Jetronic‘s so-called “mixture adjustment screw“. Before you turn it counterclockwise – which would further increase the already excessive AFM play – did you make sure that your California version CIS-ECU is switched to duty cycle output !?

If not – refering to the push button and the LED on diagnostic coupling X92 (see page 92 of 07.3-0121) and based on how I understand it – I suggest to do the following (with "ignition on", engine not running):
- push the button for 2-4 seconds
- if there is a fault code stored, the LED flashes, depending on the fault, a number of times
- then the LED stays on
- push the button for 2-4 seconds again
- if there is another fault code stored, the LED flashes a number of times again
- then the LED stays on again
- push the button for 2-4 seconds again
- if there is no more fault code stored, the LED will neither flash nor stay on … which indicates that the ECU is switched to duty cycle output to X11

Then follow post 2 of https://www.benzworld.org/forums/w126...uty-cycle.html … at least up from “Preparations“ closely again and report the results.

Even if “Vp3 while idling is about what vp6 while idling is“ again – don‘t turn the adjustment screw counterclockwise !

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post #96 of 174 (permalink) Old 12-21-2017, 04:07 PM Thread Starter
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Ah yes.. I had forgotten to do that.
I have now adjusted it, and the voltage is fluctuating between about 7 V and 7.6 V where battery voltage is 13.85. This ony amounted to about a quarter turn clockwise, and the play in the AFM is only slightly less than what it was before. I have been using the tangent of the AFM furthest from distributor as a reference for measurements, and this is the point the play would be most exaggerated. Depressing the AFM or throttle with the engine off but the key in the on position still does nothing to the voltage between 2 and 3 on the x11. When holding the throttle to 2500 RPM the voltage fluctuated between 4.4 and 3.7
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post #97 of 174 (permalink) Old 12-22-2017, 09:28 AM
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Ah yes.. I had forgotten to do that. ...
You successfully took care of it now … and withstood the temptation to rashly touch the adjustment screw before you took care of it. …

7 - 7.6 V at port 3, while port 6 shows 13.85 V represents a duty cycle of 47.3% +/- 2.2%. If that was measured at idle, that’s good (for now).

If your measurement at 2500 RPM showed 3.7 - 4.4 V at port 3, while port 6 showed 13.85 V (?), that represents a duty cycle of 70.8% +/- 2.5%. That is too different from the value at idle !

The AFM play is actually checked below the AFM’s stop bar (at the plate’s center distance to the FD). It sounds like that play is now still about 3 mm, right ?

I have two more questions (for now):
What was the duty cycle before you changed the adjustment (at idle and at 2500 RPM) ?
Has the car ever sat for a longer time, possibly with ethanol containing fuel in the system ?

The appearance of the spark plugs immediately after a 5 minutes test drive above 2500 RPM might provide valuable insight.

Quote:
Originally Posted by codycool55 View Post
... Depressing the AFM or throttle with the engine off but the key in the on position still does nothing to the voltage between 2 and 3 on the x11. ...
Please check resistance, with ignition switched off, between ECU connector terminals:
- 13 & 2, gas pedal released and depressed
- 05 & 2, gas pedal released and completely depressed
- 24 & 2, gas pedal released and depressed

BTW, did you check the camshaft lobes ? … With your car‘s production date (11/88) and mileage I really suggest to do that.

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post #98 of 174 (permalink) Old 12-23-2017, 04:51 PM Thread Starter
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The play at center is still approximately 3mm

Prior to adjustment the voltage was cycling between about .5V and 1V so about 93-96 % at idle. I don't think I took the value at 2500 RPM

Last winter the car sat for maybe 3 months, and this winter a month or two. It is definitely a possibility that it had ethanol fuel in it during that time. Aside from that I'm not sure if it has sat.

I've attached an image of the first 5 spark plugs after driving for about 10 minutes at 2500 RPM. I left the 6th plug in just because it's a little hard to get at especially when hot. This timing was convenient as I was already driving that distance at roughly that speed, so if 5 minutes is a specific time I can redo it!

13 & 2 released: .5 ohm Depressed: 4.97k
5 & 2 I got no connection either released or depressed
24 & 2 Released .5 ohm Depressed: No connection

I have not yet taken a look at the camshaft lobes however it is on my to do list! to do this I essentially need to unbolt the top cover of the engine correct? After reading through the discussion on them I decided I'd like to replace my valve stem seals however I'm just a bit intimidated as I've never done any work "inside" an engine. Is this job a DIY one or is it better left to professionals?
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post #99 of 174 (permalink) Old 12-24-2017, 12:23 AM
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Those sparkplugs do not look that bad (depends on how many miles you have on them of course).
If your are going to open the valve cover be prepared to take the oil dripper/spreader off so you can actually see the cam details.
It is held down by two small bolts. Also get a $15 Bosch remote starter as you will need to turn the engine to see all the lobes.

If you are burning oil generally changing the valve seals do not help much. I went that route and it only improved oil consumption by 20% or so.
My valve guides were original at 180K miles. Replacing the seals takes a long time too and takes many hours.

So If you believe you are burning oil you may have to do this:
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post #100 of 174 (permalink) Old 12-24-2017, 06:13 AM
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Originally Posted by codycool55 View Post
... Prior to adjustment the voltage was cycling between about .5V and 1V so about 93-96 % at idle. ...
That‘s about what I expected.

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Originally Posted by codycool55 View Post
... Last winter the car sat for maybe 3 months, and this winter a month or two. It is definitely a possibility that it had ethanol fuel in it during that time. ...
Fits into the picture too.

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Originally Posted by codycool55 View Post
... I've attached an image of the first 5 spark plugs after driving for about 10 minutes at 2500 RPM. ... ... so if 5 minutes is a specific time I can redo it! ...
10 minutes is even better than 5 minutes. And from the appearance of your spark plugs it seems that the ignition system is now properly working, which substantiates my suspicion that the higher duty cycle at 2500 RPM is caused by contamination in the FD. … I suggest to use a good injection cleaning additive at its highest dosage for at least 2 or 3 tank fillings.

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Originally Posted by codycool55 View Post
13 & 2 released: .5 ohm Depressed: 4.97k
5 & 2 I got no connection either released or depressed
24 & 2 Released .5 ohm Depressed: No connection
There is a problem with the resistance between 13 & 2. With the pedal depressed it should be infinite. Check resistance at the disconnected TPS connector (see attached image) between pin 1 (left) & pin 2 (center):
- with the throttle closed you should see less than 1 Ω (as you did between 13 & 2).
- up form when the throttle starts to open you should see infinite resistance !

It’s not relevant for the symptoms you reported so far, but when you checked the resistance between 5 & 2, did you depress the gas pedal really completely, like I said in post 97 ? … If so, check resistance between TPS connector pin 3 (right) & pin 2 (center) with the pedal completely depressed. It should be less than 1 Ω !

Quote:
Originally Posted by codycool55 View Post
... I have not yet taken a look at the camshaft lobes however it is on my to do list! to do this I essentially need to unbolt the top cover of the engine correct? ...
That’s correct … and not difficult. But when you put it back on, tighten the bolts homogenuosly and not too much, otherwise the valve cover might get warped and the rubber gasket leaky. Don’t go over 9 Nm. If you don’t have a suitable torque wrench and you feel insecure, use a small ratchet with a hole at the end of the handle and a spring scale, if you have, and do a little math. … And make sure the gasket sits correctly in the machining notch at the rear of the cylinder head.
If you take off the camshaft oil pipe for a better view on the camshaft, be careful with the bolts when you reinstall it. The M5 aluminum thread holes can easily be overtightened !
I suggest to turn the camshaft manually by turning the crankshaft clockwise ! using a ratchet and a 27 mm socket. For easier turning you can remove the spark plugs … and use leather gloves for protection against the radiator’s rough surface.

Quote:
Originally Posted by codycool55 View Post
... After reading through the discussion on them I decided I'd like to replace my valve stem seals however I'm just a bit intimidated as I've never done any work "inside" an engine. Is this job a DIY one or is it better left to professionals?
From your spark plug images it does not appear that your engine is excessively burning oil. Check if you see engine oil leaking somewhere (see what I said in post 75 about the front cover). And check for coolant cleanness in the reservoir.

If the camshaft is worn, then I suggest to replace the valve stem seals at the same time when you replace the camshaft (& rockers), of course.
As I already mentioned in post 75 … and against other opinions … changing the valve stem seals alone might stop all excessive oil burning. The valve guides are often still in good condition, while the seals have been toast for a long time already.

Replacing camshaft / rockers and valve stem seals takes a thoroughly working and experienced (DIY) mechanic about 6-7 hours. It requires some care, of course. In order not to ruin the engine, especially the timing chain has to be put back in correct relation to the camhaft sprocket, and the chain tensioner has to be reinstalled properly. … It’s something that, in case of doubt, I suggest to have done by someone who knows how to do it and has done it before.

Merry Christmas to all readers !

H.D.
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