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  #1  
Old 01-12-2002, 10:31 AM
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Unhappy Idle problem - 94E320 HELPPPP

First of all, I would personally like to thank Gillybenztech for assisting me with this problem. Last week, I had an emissions problem so I had the air mass sensor changed. The cars idle fluctuated from 500-1000 rpms in the park position only, otherwise ok.

After having that part installed, the idle stopped fluctuating in the park position. But then I got an irratic idle. THE IDLE WAS FLUCTUATING FROM 500-700 RPM AT A STOP SIGN OR RED LIGHT IN THE DRIVE POSITION WHEN STANDING STILL. Sounds like "VRM VRM VRM VRM". When the car accelerates it's fine. The car surges forward then back only when I'm standing still. After 10 seconds or so It would stop.....the car gives up!!!! I can still drive but at the stop sign or red light I have to put the car in neutral.

The damage....idle speed conrtol unit....02 sensor $1,450.00. I've read on the boards that I might not need one. I know that I will need to spend money on this one but certainly not $1,450. The 02 sensor is not directly related...that's for emmisions.

Throttle Actuator?? self adaptation?? engine wire harness??air slide valve??? used tested idle control unit????

The car 99K on it. The car is at the shop waiting for my decision on Monday Jan 14.

Thanks,
Ron

Last edited by RonE320; 02-14-2002 at 12:42 PM.
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  #2  
Old 01-12-2002, 10:41 AM
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BY you description I would say the throttle actuator is defective. List price is $1,100.
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  #3  
Old 01-13-2002, 02:14 PM
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Location: Mableton, Georgia
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Welcome to my nightmare. Had same problem last week- required Wiring Harness, and Throttle Actuator. Dealer paid parts cost on Wiring Harness, but I'm still out $1500. This after having a water pump and Battery replaced last week. Lousy track record for a garaged, Dealer serviced '94 E320 with 86k on it. This is my 3rd MB, but it may well be my last.
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  #4  
Old 01-13-2002, 09:05 PM
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davey I totally understand what you went through. I guess that the idle control unit and the throttle actuator are one of the most expensive parts to replace. my mechanic says thats its the ICU.
I will definately mention the throttle actuator. I guess hell test it.
my rough first month!!!
could someone explain in a few sentences the function of throttle actuator. Is this also called throttle motor?

"Theres always a better way"
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  #5  
Old 01-13-2002, 10:05 PM
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Location: Suwanee, GA, USA
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I have tested and replaced many of the throttle actuators and none of the control units. The throttle actuator is an electronic accelerator of sorts. It controls idle, cruise and accel functions. One easy way to test is to see how well the cruise works. An ill cruise system is an early indicator of a faulty throttle actuator on the 104 engine.

I would test this circuit then cut open the throttle actuator harness to see the wires inside. My bet is that they are faulty.
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  #6  
Old 01-13-2002, 11:17 PM
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Hi Ron:
The throttle motor is part of the actuator, it's all one assembly though. In it's simplest description, it controls the throttle (the butterfly valve in the venturi). They went to this when they wanted to incorporate control of the throttle into the anti-skid control (traction control). They figured "what the heck, lets do it electronically all the way, then we can use it for idle control and cruise control too". My experience on bad ones has been mostly with the 119 motor V8, the 104 motor I can't recall replacing one personally. I think the heat gets to them on the 119 motor, it has to get hot practically buried in the valley between the heads. Usually they are going into a back-up mode called "limp home mode", either that or they idle bad like yours is.
I still maintain that since it works OK off idle, not in limp-home mode, and that the air mass meter was replaced, that the tech may have reset the self-adaptation of the fuel trim and neglected to reset the throttle stop position. I believe that on these, you erase the throttle valve stop (electronically) when you reset the self-adaptation. Maybe the tech is unfamiliar with this procedure and started learning the throttle stop, thought it was done and removed his scanner early? Given the scenario, I would "back up" and look things over more closely, at least try having the throttle stop relearned before going this route. Just to much "coincidence" for me to start ordering parts already.
Gilly
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  #7  
Old 01-14-2002, 12:49 AM
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good points gilly and donnie. thanks. I will look into the self adaptation and check the wireharnesses. If it isn't good I will have Mercedes replace it under warranty. $500 otherwise.

the problem is that this mechanic is the shops owner...20yrs+. he said he pulled the codes etc. Hence idle control box or unit. He might actually mean the throttle actuator because he said its the box that controls the cruise control etc. You guys feel its the throttle actuator. I'd like to go with you on this one. I read in one of your posts that you have never replaced the control units and that you could see this only if the throttle actuator is faulty and it blew out the computer. You also mentioned that if you replace the controller without the actuator then it will eventually blow too.

so now you see I'm a little worried. He puts in the new unit and a month later the faulty actuator messes it up.

either way it looks like a big job. well now ill be prepared for tommorows showdown!!! I'll keep you all posted...stay tuned
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  #8  
Old 02-18-2002, 03:11 PM
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Well eventually I had the throttle actuator replaced but that did not solve the problem so my mechanic removed it. He installed a new Engine wire harness becuase he felt that both parts died at the same time.

Problem still not solved. The computer is now showing that the idle control unit is faulty. One of the most expensive parts for this car and it has to be programmed at the dealer.

We will first install the actuator and see what happens. The dealers in my area would not install the harness under their good will policy.

Has anyone else been through this? Any thoughts?
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  #9  
Old 02-18-2002, 10:54 PM
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Ron:
I'm confused as you state you will "first install the actuator and see what happens". You said you had the actuator installed and it didn't fix it.
I still maintain, unless the mechanic states otherwise, that the throttle stop may not have been learned. They will run like this if the stop isn't learned, and this could all go back to when the air mass sensor was replaced. If he reset the adaptation and didn't relearn the throttle stop it will run like this.
Does the mechanic say there are now codes indicating a faulty EA control module, or does he just "think" it needs a new EA control module?
Gilly
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  #10  
Old 02-19-2002, 09:06 AM
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Gilly,

He just put in a new wire harness. Before he just put in the actuator or air slide without the wire harness.
So now he wants to put the actuator back in.
But the EA control mdule is showing faulty code....a $1,200 part.

I heard in the past that the diagnosis machines are sometimes wrong.
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  #11  
Old 02-19-2002, 09:21 AM
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I am pretty sure that he relearned the throttle stop. I will double check.

Buy the way, does the EA control module need to be programmed at the dealer?
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  #12  
Old 02-19-2002, 10:37 PM
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Ron:
Usually the codes aren't really "wrong", but alot can be left up to interpretation.
See if you can find out what the code is in EA and myself or Benzmac can tell you what we think.
My thought is that the mechanic may be thinking "lets see, it wasn't the actuator, it wasn't the harness, hmmmm, must be the control module". I can't say that's what's going on for sure, just makes you wonder though.
Gilly
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  #13  
Old 02-20-2002, 06:50 PM
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Gilly and company:

We just installed the air slide valve or actuator. We decided that since idle control units rarely go bad we decided to replace the air slide. To update a new engine wire harness was put in a few days ago.

Still the problem exists - irratic idle. The computer is showing Idle control module faulty code... but I Did not see it. Since he cannot program the module he is recommending that it be taken to the MB dealer.

We have not decided if we are going to remove the actuator.

Ron
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  #14  
Old 02-20-2002, 07:13 PM
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Ron:
Go ahead and take it in. I'd like to help, it sounds like no one on that end is listening to my suggestion about learning the throttle stop, I still maintain that this may be the only problem. Maybe the guy doesn't understand this needs to be done when replacing the throttle motor (throttle slide=same thing, tech definition vs. part definition). When he went back to the original, it needed to still be relearned. I think he's chasing his tail now. When the throttle stop is not learned, it will drive OK, except when coasting or at idle, it won't idle correctly.
It may learn it by itself if you just turn the key to "ON" and wait a minute of 2, or it may have to be put in to the learning mode, it seems like this varied from system to system. If it's learning it you will hear a strange electrical motor sound (like a whining or high pitched buzzing) as the electric motor runs the throttle plate from one stop to the other.
I am especially skeptical because now he seems to be backing down from his assertion that the EA control unit is bad and suggesting the dealer. If he has a fault code for a self-diagnostic failure of the EA control unit, why not accept it and order the control unit? I'm sorry, I don't know if this needs to be adapted to the specific car or not, but I do know you sure as heck will need to learn the throttle stop!!! Also why didn't he give you the fault code that is telling him that the EA control unit is faulty? "You didn't see it" makes me think "He's bluffing". Good Luck!!!
Gilly
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  #15  
Old 02-20-2002, 08:10 PM
toyberg
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Same Problem!!! Same year!!! Same diagnosis

I am having the same problem. My car is hard to start unless I keep my foot on the gas. Stalls in stop and go traffic if the A/C is on, no A/C...runs fine but idles low and surges occasionaly but no stalls. I just got it back from the shop and the Tech said the Cruise Control/Idle module (P/N 0001415725) is the problem. I did not see nor did he provide the code. The cost is $750 for the part (new) and about $275 Labor. This has been going on for quite sometime and for that kind of $$$ I figure I can live with it for now. Just had the wiring harness done for $750 and this car is starting to become a money pit. New Alternator $550. Motor Mounts $280. Belt Tensioner more $$$. On top of my $500 + car payment (paid off in July) you can see my frustration. I feel your pain! BTW, I found one of these units on a slavaged car for $400 w/ 90day warranty.
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