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  #1  
Old 04-06-2012, 01:38 PM
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Join Date: Jun 2002
Location: Motor City, MI
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95 E320 rough running

When I started the car yesterday, the engine suddenly developed a vibration. This vibration is with the engine at all speeds. I thought I was running on five cylinders. I tried to diagnose the problem by disconnecting each injector to find the missing cylinder, but this isn't the case. The engine runs rougher each time I disconnect an injector. What could be causing this vibration?

No check engine light came on. I went to read the codes, and interestingly, the #2 LED light was on, and there is no response to testing. Perhaps related?
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  #2  
Old 04-06-2012, 05:12 PM
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Join Date: Apr 2012
Location: Minneapolis, MN
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Maybe weak spark from either bad wires or a bad coil. Was it a wet day for you yesterday? maybe try spraying some water over the wires and see what it does... Oh, also, sometimes the valve covers leak into the spark holes and fill the wires with oil. Pull up the coils and wires and check for oil puddles in top of the plugs.
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MB Star certified, now independent.
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1998 E320 4MATIC-- stolen by my sister
1989 300TE-- sold
1999 C230 Kompressor
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  #3  
Old 04-06-2012, 07:40 PM
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Quote:
Originally Posted by fdm_alex View Post
Maybe weak spark from either bad wires or a bad coil. Was it a wet day for you yesterday? maybe try spraying some water over the wires and see what it does... Oh, also, sometimes the valve covers leak into the spark holes and fill the wires with oil. Pull up the coils and wires and check for oil puddles in top of the plugs.
i had this in my car..and replaced the 3 coil wires.... never had an issue again
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1989 300ce 129k
( facelifted front,updated tail lights, lowered suspension,bilstein sports, lorinser front spoiler, MOMO steering wheel, remus exhaust,stainless steel brake lines). (Gone)

1997 s320 154k (what a ride)

1994 e320 Cabriolet 98k (finally)



1972 280se 4.5 153k Owned for 12 yrs, sorry I sold it


[/SIGPIC]
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  #4  
Old 04-06-2012, 07:53 PM
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That's what I thought - a bad coil. But why doesn't the dead cylinder present itself when I disconnect the injector?
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  #5  
Old 04-06-2012, 08:07 PM
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Sometimes an engine vibration is just a bad motor mount.
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2001 E430, Bourdeaux Red, Oyster interior.
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  #6  
Old 04-07-2012, 05:19 AM
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Kestas, I had a similar problem with our 1995 E320. Turned out to be a bad coil pack. Bought a new coil pack and swapped it into the 3 different coil locations ... the rear coil pack was the bad one. If you find that the engine mounts are collapsed recommend buying replacements from a MB dealer because some aftermarket mounts are inferior quality and fail quickly.
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  #7  
Old 04-07-2012, 10:09 AM
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I would think at all speeds would point away from motor mounts. I'd suspect the 16 pin problem may be related, in any case it's a good place to start so that you can read the codes. Wiring diagram for the data link connector is here - http://www.autolib.diakom.ru/CAR/Mercedes-Benz/1995/E320/SYSTEM%20WIRING%20DIAGRAMS/ One thing that sticks out is that pin 16 power comes from the OVP relay.
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  #8  
Old 04-07-2012, 11:25 AM
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Location: Motor City, MI
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I'll ignore my attempt at diagnostics and go ahead with new coil packs (and wires). It just makes too much sense to think it's anything else. At 107K all ignition parts are original. It won't be money wasted.

I'll be going with Bosch for the parts. Beck Arnley is a second choice. Other choices (cheaper) are Delphi, Bremi, and Prenco.

The OVP was updated long time ago. I should also mention the engine wiring harness was replaced nine years ago and shouldn't be an issue.
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  #9  
Old 04-16-2012, 12:29 PM
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Fixed! I replaced all three coil packs, wires, and connectors. $240 later the problem is gone.
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  #10  
Old 04-16-2012, 02:21 PM
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Quote:
Originally Posted by Kestas View Post
Fixed! I replaced all three coil packs, wires, and connectors. $240 later the problem is gone.
good feeling isn't it?
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1989 300ce 129k
( facelifted front,updated tail lights, lowered suspension,bilstein sports, lorinser front spoiler, MOMO steering wheel, remus exhaust,stainless steel brake lines). (Gone)

1997 s320 154k (what a ride)

1994 e320 Cabriolet 98k (finally)



1972 280se 4.5 153k Owned for 12 yrs, sorry I sold it


[/SIGPIC]
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  #11  
Old 04-19-2012, 09:39 PM
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I didn't see any mention of you pulling codes. The $15 Radio Shack parts code tester is what I'm talking about.

If you'd have pulled the codes from the car, it would have told you WHICH of the three coil packs had gone bad. Not that replacing all 3 is a bad idea, but you can indeed pinpoint it down to the specific pair of cylinders that have the bad pack.

Cheers,
Gerry
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  #12  
Old 04-21-2012, 11:43 AM
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I've had 4 separate instances of rough running that were corrected with a coil swap. In all 4 cases, no codes were present. Is it possible for a coil to be "weak" enough to cause run problems, but not weak enough to trip a fault code? Are there certain types of coil failures that don't trip fault codes?

As a side note, the coil to plug "boot" type connectors are also a known common failure item. They are cheap enough that I replace them any time I have run problems, change plugs, etc......

J. M. van Swaay
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