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Discussion Starter #1
Good day Mercedes Benz enthusiasts,

My name is Zeki and I just joined this forum recently. I'm hoping to learn more about these beautiful cars and benefit from your advice.

I am Namibian and live in Botswana. My W140 Benz S500 coupe stalled as I was driving to Johannesburg about a year ago.
I slowly returned to Gaborone. I could not go faster than 30km/h. Any attempt to go faster would result in a "cut" - as if
a supply of something essential like air or fuel breaks down and then a rough and disturbing movement follows.
When I took it for diagnosis, they used a machine and the test result pointed to the MASS AIR FLOW SENSOR (MAFS). They advised me to buy a new
sensor. But I could not get it locally. So, I cleaned the one I had in the car using a mass air flow sensor cleaner, after which I drove the car for about 260 km (~162 miles) but then the problem reoccurred. Next, I ordered a (used) mass air flow sensor from USA through eBay and got it fitted, but this didn't solve the problem.
I got a few suggestions that led to replacing the fuel filter, fuel pump, ignition control module and the mass air flow sensor again. The problem still stands. I can only move it at 20km/h or so and I really miss the smooth ride in the S500 on a highway. Any similar experiences? Any advice?
 

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W124 Moderator
86 190E 2.3L 16V, 2 95 320TE's, 02 S500
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What year is the car?

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The registration documents say 1997. But when I give the Mercedes Benz agents
the VIN for parts they say it is a 1994 model.
 

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W124 Moderator
86 190E 2.3L 16V, 2 95 320TE's, 02 S500
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Chances are strong that your upper and lower wiring harnesses and throttle actuator are original. As such, they are made up of the biodegradable insulation material on the wires. There are untold number of threads on this subject. To solve your problem, you'll need to replace the throttle actuator and harnesses. Otherwise you'll just be chasing ghost.

Good luck

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94 - S500 Cpe
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My W140 Benz S500 coupe stalled as I was driving to Johannesburg about a year ago.
If it's a '94 S500 (as is mine), then Jayare's suggestions should be followed. The engine wiring harness MUST be replaced as well as the ETA.

But before you do that, I suggest that you read the Diagnostic Trouble Codes (DTC) stored in the car's various modules. You can build a code reader here in the "Home Brew DTC Tool" section that will allow you to read the stored codes. Or you can purchase one here

The '94 S500 used a "Hot Wire" MAF sensor and they are pretty much indestructible. Mine is original and still going strong.

We can help you arrive at a cost effective solution.
 

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1994 S320, S 600 1994 , SL 600 1999
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I had the same problem, I am sure it is your ignition system.Please check,
1) Spark plugs
2) Spark plug cable set
3) ignition rotor caps
4) coil
 

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Discussion Starter #7
Chances are strong that your upper and lower wiring harnesses and throttle actuator are original. As such, they are made up of the biodegradable insulation material on the wires. There are untold number of threads on this subject. To solve your problem, you'll need to replace the throttle actuator and harnesses. Otherwise you'll just be chasing ghost.

Good luck

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Jayare,
Thank you very much for your response and good suggestion. I will discuss this with the mechanic who will work on the car.
 

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Discussion Starter #8
If it's a '94 S500 (as is mine), then Jayare's suggestions should be followed. The engine wiring harness MUST be replaced as well as the ETA.

But before you do that, I suggest that you read the Diagnostic Trouble Codes (DTC) stored in the car's various modules. You can build a code reader here in the "Home Brew DTC Tool" section that will allow you to read the stored codes. Or you can purchase one here

The '94 S500 used a "Hot Wire" MAF sensor and they are pretty much indestructible. Mine is original and still going strong.

We can help you arrive at a cost effective solution.
Dear JimF37,
I have no idea how to thank you for your contribution. What does ETA stand for, which you suggest should also be replaced?
 

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Discussion Starter #9
I had the same problem, I am sure it is your ignition system.Please check,
1) Spark plugs
2) Spark plug cable set
3) ignition rotor caps
4) coil
Dear Dido,
Thank you very much for your suggestion. If I remember correctly, spark plugs were also replaced at some stage, but I will certainly get everything checked again.

Did you replace any of the parts 1) - 4) when you experienced the same problem?
 

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Dear JimF37,
What does ETA stand for, which you suggest should also be replaced?
That PROBABLY needs to be replaced (Jayare's suggestion) but to be sure have the stored codes DTC read out . . . your tech s/b able to do that.

To read more on the ETA (Elec Throttle Actuator) check out this link here There's a lot a diagnostic info on it in the link plus others that have problems and where they were repaired/replaced.
 

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1994 S600 Coupe, 1995 S600 Coupe
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1,782 Posts
Dear JimF37,
I have no idea how to thank you for your contribution. What does ETA stand for, which you suggest should also be replaced?
ETA is the electronic throttle body. The insulation on the wiring flakes off and shorts things out on 92-95 model year cars. Yours may have been replaced already, or could be bad. Only way to tell is to cut open the sheath around the wiring and check.

Jon
 

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W140 Moderator
"CHRIS" Merc 92 600SEL / Sold > 93 600SE / 93 S500 / 89 560SEL / 413CDI / B180-CDI /A170-CDI
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So basically your car is in Limp Home Mode . On the cluster you should have either 1 or 2 yellow lights on ,correct ?. I'm not ruling out the wiring has disintegrated but there could well be a different fault . 1st thing you do is clean the ABS speed sensors at the front wheels ,see what happens . Next check your ICM (Ignition Control Module) on the Fender underneath the engine covers on the side ,they go defective on early 140's ,you're in for a lot of trouble . Have you checked all your Fuses & Relays UNDERNEATH the Fusebox that they are in order ?.
On the side of the Transmission there are a few airhoses ,if one of them has come of or looses air pressure like i had ,the car runs horrible (just to mention) .
Posting a picture of your car since you not sure what year it is ,would help ,we know by just seeing a few options it has what year model it is 99%,even just seeing a mirror tells me everything ,no need for the BS from Dealers guessing game etc .
BTW : Disconnect the MAF if you suspect it ,see how the car behaves driving without .
You don't buy delicate parts for a w140 like a MAF sensor 2nd hand ,buying 2nd hand from wreckers unless you know the car the part comes from ,all you doing is buying the same defect again .
Check your Distributors /fuel pump/fuel pressure regulator /fuel pump relay/change fuel filter & of course before anything ,check the engine wiring's all over ,specially leading to the ECU box near the firewall .
 

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Discussion Starter #14
Yes, I also thought this must be a Limp Home mode (LH-M) I read about in the link JimF37 referred me to.
The light which is ON is an SRS light but this has been on for more than 5 years before this problem started.

I think that's a good point regarding used parts like a MAF sensor for a W140.
The Ignition control module has been replaced. The tricky part of this problem is that one is not really sure what the root cause of the problem is and which part is faulty. So one can replace a number of parts in the process.

I just uploaded one picture of the S500. Sorry It's not very clear but I'll get more later.
Chris(?), I've taken note of the things you said should be checked.
Thank you.

I'm glad I joined this forum. There isn't only knowledgeable people but a lot of kindness and generosity.
 

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The light which is ON is an SRS light but this has been on for more than 5 years before this problem started.
The SRS light should have NOTHING to do with the poor running performance.

Check out the info here at the bottom of the page "SRS Light is On". A MB tech should be able to RESET the SRS system w/ a scan-tool and turn the light off. However, if there is a HARD failure, bad air bag, failed selt belt extender, the SRS will come back on.

A number of years ago, my SRS light came on and it was a "dirty" contact in the front - driver's side seat belt; cleaned it and the SRS went off. You might try cleaning all your seat belt extenders. Can't hurt.
 

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W140 Moderator
"CHRIS" Merc 92 600SEL / Sold > 93 600SE / 93 S500 / 89 560SEL / 413CDI / B180-CDI /A170-CDI
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The things to check ,most of them are easy like cleaning abs sensor ,cost nothing to clean . Only later if the fault dosent go away it gets expensive .
Yes a lot of friendly members here but only until you mention W220 ,then you need to run ,lol. SRS light resets with scanner tool if all is good like Jim mentioned ,i did that recently on a friend of mines S600.
 
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