Engine sometimes runs rough & R powerless - Mercedes-Benz Forum

 
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post #1 of 7 (permalink) Old 01-21-2008, 10:44 AM Thread Starter
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Date registered: Oct 2006
Vehicle: S600 C140 1994
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Thumbs up Engine sometimes runs rough. SOLVED!

Car: MB S600 1994 coupé

Done so far:

New engine harness.
New ETA-wiring.
Cleaned MAF's.

Problem:

Sometimes, about 3-4 times a week the engine gets in some kind of "limp mode". Really rough idle (almost shakes) and feels powerless and tired. I only notice this at very low speeds or on idle. I also can hear a change in sound from the engine.

After I've turned the engine off and restart it the problem is gone.

I notice it at red lights or other stops like on the drive way.

What could it be?

Thanks! / Jonathan Wallin




~C140 S600~
http://www.garaget.org/?car=34361[/url]

Last edited by Jonathan Wallin; 01-27-2008 at 07:20 AM. Reason: Problem solved!
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post #2 of 7 (permalink) Old 01-21-2008, 07:15 PM
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Vehicle: 2001 MB S600, 2005 BMW X5 4.4i, 2002 Chevy Avalanche (Canada) 1996 BMW 750iL, Smart 4 2 (France)
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Engine sometimes runs rough & R powerless

On my 2001 S 600, it turned out to be the Crankshaft position sensor going intermittent. It would go OK for about a 1/2 hour, then it would run rough. after a few days of doing this, it just up and quit. Stone dead. It would just crank away, with no ignition at all. Had it towed in to MB and by the time they got to it (2 days later) it started just fine. After checking out various things they took it for a drive and it started acting up. The funny thing is that there was no code in memory.

To make a long story short, they replaced the engine wiring harness (on Warranty), the oil pressure sensor (it leaked oil past the electrical contacts and filled the harness with oil), 3 O2 sensors, the crank position sensor and some various other recall stuff on the hydraulic suspension system.

I was without the car for a week and a half but when I got it back it ran great and with all the power it had before. Gotta love that V12.

I hate to think how many thousands this would have cost, with 2 techs and over 40 hours plus parts, but MB Canada covered the whole thing, and gave me a courtesy car as well.

As it turned out, the oil pressure sender was under recall and the resulting damage was covered by MB because I had not been notified of the recall (being the second owner).
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post #3 of 7 (permalink) Old 01-22-2008, 02:07 PM Thread Starter
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Great story with a great ending!!

My car runs fine most of the time. About three times a week this "problem" comes up.

After a restart its gone.

I'm planing to take the car to the machanic to get a diagnos. They know how to search.

~C140 S600~
http://www.garaget.org/?car=34361[/url]
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post #4 of 7 (permalink) Old 01-27-2008, 07:17 AM Thread Starter
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Problem solved!

It turned out to be the passenger side MAF-sensor thats not working as it should.

It could be the MAF itself or the wires to it.

This is what the wires looked like:




Yesterday I ordered new high temp. wires to rewire with.

Thanks!

~C140 S600~
http://www.garaget.org/?car=34361[/url]
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post #5 of 7 (permalink) Old 01-27-2008, 12:53 PM
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I believe the 1994/1995 German cars had a problem where the entire wiring harness was junk. Your wiring looks like an OEM harness that has deteriorated. If your harness is original, wouldn't you want to replace the engine wiring harness?
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post #6 of 7 (permalink) Old 01-27-2008, 02:20 PM Thread Starter
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Hi!
I have allready replaced the injection wiring harness (engine harness), ETA-wires and now I'm going to rewire the MAF's too.

MB had these cabels in their models from 1991 to 1996.

This feels sooo good to do.

No more rough run or unreliable engine.

Is this "cable-problem" common on other Mercedes cars from the 90's?

~C140 S600~
http://www.garaget.org/?car=34361[/url]
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post #7 of 7 (permalink) Old 03-28-2008, 12:01 PM Thread Starter
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The rough run/idle didnt go away after the rewiring MAF and ETA's.

BUT!

The problem is now solved!

The problem with the rough run/idle had to do with the driver side rotor. It has a resistor (spelling?) inside that was broken. This made the engine some times run on only 6 cylinders.

I had no spark on half the engine.
This made me concentrate to one of the coils and also the distributer on that engine half.

I ended up with a broken rotor. I used the multimeter on it and it pointed to that same conclusion.

This week I'll order two knew distributors and also two new rotors.




~C140 S600~
http://www.garaget.org/?car=34361[/url]
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