M103 Rough idle and vacuum leak - Page 14 - Mercedes-Benz Forum
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post #131 of 174 (permalink) Old 03-31-2018, 08:35 PM Thread Starter
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Hello again everyone! I apologize for falling off the face of the planet, I just finished up a very busy quarter including differential equations and international robotics competition. This next quarter should be a (Relatively) lighter load, allowing me to give my car the TLC she needs. I'd love to have her ready for some summer road trips.

Back to the inquiries from @H.D. The camshaft appeared to be in good condition. There were no noticeable signs of wear to me or a friends parent with a lot of automotive experience.

In regard to testing resistance between terminal 13 and the other terminals here's what I found. If I didn't list a terminal I did not get a connection
1 - 10.8k
2 - 4.9k
9 - 513k
16 - 4.9k
19 - 8.6k
20 - 4.9k
23 - 10.8k
24 - 4.9k
25 - 50k
the test was taken with the tps disconnected.
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post #132 of 174 (permalink) Old 04-01-2018, 12:13 PM
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Hello Cody, good to see you again.

Quote:
Originally Posted by codycool55 View Post
... I just finished up a very busy quarter including differential equations and international robotics competition. ...
That‘s interesting. … I give extra tuition in “Engineering Mechanics“ to mechanical engineering students at the technical university in my home town, one of the most popular technical universities in Germany and visited by students from all over the world. And EM (with its subdivisions kinematics & kinetics, which differential & integral calculus plays a role in, of course) is the most important subject for engineers who want to get their teeth into the mechanical part of robotics. …

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... The camshaft appeared to be in good condition. There were no noticeable signs of wear to me or a friends parent with a lot of automotive experience. ...


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Originally Posted by codycool55 View Post
... In regard to testing resistance between terminal 13 and the other terminals here's what I found. If I didn't list a terminal I did not get a connection
1 - 10.8k
2 - 4.9k
9 - 513k
16 - 4.9k
19 - 8.6k
20 - 4.9k
23 - 10.8k
24 - 4.9k
25 - 50k
the test was taken with the tps disconnected.
Okay … remember when I said (in post 108) “the wire of terminal 13 might have a (5 kΩ) connection to engine ground via some other path“ and I suggested the resistance measurements you report now? … Although doubts about the meaningfullness of this suspicion were signaled (in post 121), it‘s what seems to be the case here. …

With the TPS disconnected and ignition switched of, there should be infinite resistance (no connection) between terminal 13 and all other ECU connector terminals, except terminal 25. However, are you sure you measured 50 kΩ between 13 & 25, and not 5.0 kΩ ?

Now, as a first step to find that path, I suggest to do the above 9 measurements again, however, with the 4-terminal EZL plug above the CPS plug disconnected too. If you‘re not sure which plugs I‘m talking about, simply disconnect both 4-terminal EZL plugs.

Happy Easter to all! …

H.D.
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post #133 of 174 (permalink) Old 04-08-2018, 03:57 PM Thread Starter
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It was indeed 50k ohm between 25 and 13. With the TPS and both ezl plugs disconnected I registered no connection between 13 and any other pin.
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post #134 of 174 (permalink) Old 04-09-2018, 07:23 AM
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... With the TPS and both ezl plugs disconnected I registered no connection between 13 and any other pin.
… You see! The search for this “other path“ I suggested to find in post 108 seems to have been more meaningfull than commented in post 121. …

According to the results you reported, it seems this “other path“ goes via EZL. There seems to be a short in the EZL. Can be tested with all plugs disconnected, of course. There should be no connection, neither between EZL pin 2 and any other EZL pin, nor between EZL pin 2 and ground ! (EZL pins are labed)

In post 104 you said: “ … the main symptom I'm still having is a lack of power before the car heats up. The engine seems very bogged down … "
If you‘re lucky and there are no other preventing issues, that will be remedied after taking care of the EZL problem.

However, even with a new EZL the power at WOT (fully depressed gas pedal) will probably still not be as strong as it should be, because according to what you reported in post 101 there is a problem with the TPS‘s “throttle fully opened“ signal. Either the TPS (which is a double switch, one for "throttle closed" and one for "throttle fully opened") is faulty or the fully opened contact is not switched with the gas pedal fully depressed, which can be caused, for instance, by an incorrectly adjusted throttle linkage.

In post 108 I said that I‘d come back to the not working cruise control you reported in post 104 (and other possible problems) later. … If you‘re lucky, cruise control will also work again after taking care of the EZL problem. …

H.D.
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post #135 of 174 (permalink) Old 04-16-2018, 06:39 PM Thread Starter
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Unfortunately pin 2 has connection to all the other pins, except for TD. Here are the resistances in kohms

Ground-5.2
1-5.6
3-5.6
4-9.3
15-430
16-12.9
31-5.2

Once again HD, thanks for all the help. This is a path I would have never went down without your guidance.If you don't mind, can you explain the purpose of the EZL? My understanding is it adjusts the variable timing but I'm sure there's more to it than that!
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post #136 of 174 (permalink) Old 04-17-2018, 12:33 AM
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Unfortunately pin 2 has connection to all the other pins, except for TD. ...
Bingo!

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... Once again HD, thanks for all the help. This is a path I would have never went down without your guidance. ...
You‘re welcome! …

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Originally Posted by codycool55 View Post
... If you don't mind, can you explain the purpose of the EZL? My understanding is it adjusts the variable timing but I'm sure there's more to it than that!
In the non-German speaking world the abbreviation “EZL“ is usually incorrectly used for the ECU that controls the ignition. “EZL“ is the abbreviation for “Elektronische Zündanlage mit Zündlinienverstellung“ (electronic ignition system with variable ignition timing). That‘s the name for the entire ignition system. In order not to cause unnecessary confusion here at Benzworld I use the abbreviation “EZL“ - with an odd feeling - for the system‘s control unit too.

The EZL gets a number of electrical input signals & input about the intake vacuum level, based on which it recognizes the engine‘s operating condition and determines the ignition timing. One of the input signals the EZL not only uses for the ignition timing. The one from the CPS (Crankshaft Position Sensor) is converted into the “TD signal“ which represents the engine‘s speed and is also sent as input signal to other components (FPR / MAS, CIS-ECU, idle control unit).

The input signal that arrives at pin 2 of your EZL‘s control unit is the TPS‘s “throttle closed“ signal. … In other words, the wire that carries the TPS‘s “throttle closed“ signal to the CIS-ECU is always connected to the wire that carries the same signal to the EZL‘s control unit, no matter whether the TPS connector is connected or not. … And that‘s the other path I had (mainly) in mind and repeatedly mentioned up from post 108 in order to trigger an “aha moment“ among the readers of this thread. …

BTW … this is a perfect example why I always suggest to first check sensor signals at the connector of the component that processes them (ECU, FPR, MAS, EZL, idle control unit, …), not at the senor itself ! … People who would have checked the TPS‘s “throttle closed“ signal only at the TPS connector, where it worked perfectly, would probably have thought that everything is okay with it and never have found out about this problem … and possibly thrown many more parts at it. …

H.D.
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post #137 of 174 (permalink) Old 04-17-2018, 01:07 PM Thread Starter
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So now that we've found this problem how can we solve it? Is a replacement of the EZL necessary, and can a used one (junkyard or otherwise) suffice? I've done a little bit of searching but I haven't been able to find a replacement. Although I definitely could have searched more.
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post #138 of 174 (permalink) Old 04-18-2018, 03:08 AM
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These posts are very good and full of information for everyone , and for myself . .And every forum needs someone like HD with his ability to give step by step tutorial . And in the past i have told others if they do not have a stand by EZL then now is the time to get one . And as soon as you pick one up then try it on the car right away . Dont wait till the EZL as gone down only to find the one you picked up is faulty as well . The price for these over here are going up .Last one i saw was £500 second hand they are rare as hens teeth .
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post #139 of 174 (permalink) Old 04-18-2018, 08:07 AM
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So now that we've found this problem how can we solve it? Is a replacement of the EZL necessary, and can a used one (junkyard or otherwise) suffice? ...
Yes, if you can find one at a junkyard I suggest to try it. … With 45 quick resistance measurements you can do the following test already at the junkyard (takes less than two minutes):

With all plugs disconnected there should be no continuity between any of it‘s 10 terminals (including the coaxial terminals for the CPS plug) … with one exception: between terminal 31 & the outer coaxial terminal for the CPS plug should be full continuity.

If you can‘t find one at a junkyard I suggest a search on ebay.

There are companies which offer EZL repair, but that‘s usually more expensive than good used ones.

Don‘t forget to put heat sink compound on the EZL‘s mounting surface !
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post #140 of 174 (permalink) Old 04-18-2018, 12:35 PM
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These posts are very good and full of information for everyone , and for myself . .And every forum needs someone like HD with his ability to give step by step tutorial ...
Thanks for the compliment, panzernacker.

My contributions are not suitable for every forum, though. For instance, they‘re not suitable for Benzworld‘s 124 forum.
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