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1993 MB 300E 2.8
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Discussion Starter #1
Hi all,

I recently replaced the valve cover gasket and spark plugs on my 1993 300E 2.8.
I test drove it and drove it around for a while and I had no issues, but one day a family member was driving it and needed to slam on the brakes when cut off by someone. They said that after that the car ran quite rough, stumbling at idle and sometimes also at throttle. I got under the car to see if anything was out of place, and I noticed this (what I believe to be a vacuum line) disconnected. The pictures I posted show what the line connects to at the top of the engine bay, near the oil dipstick (circled). I'm honestly not sure what it should be connected to on the underside, and I also don't know what it's connected to. Any help with this info would be very much appreciated! Thanks!
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Premium Member
2014 G550, 2000 SL500, 1995 E320 Cabriolet, 1980 TR8
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1,387 Posts
Hmmm, interesting. I'm not sure, but could be a disconnected evap line? Try temporarily plugging the line in the picture and see if your issues resolve. If not, maybe an ecco junk wiring issue (damage by the sudden maneuver)?
 

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1989 W124 260E
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1,888 Posts
I would say that the vacuum line is the problem . With just rubber hose on it looks like its come off the inlet manifold .
 

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1989 W124 260E
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1,888 Posts
Check the other end to see wher it goes ..Looks like the vacuum pipe is from the inlet manifold and if it goes to auto box
 

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W124
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5,300 Posts
Check to see if the vacuum line is still connected to the vacuum modulator on the transmission. If not, this is it. Also, I would have the transmission and engine mounts checked because something shifted mightily when the brakes were applied during that panic stop.
 

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1990 Benz 300E 2.6 (mine) ; 1994 E320 Wagon (wife's) ; 1993 300CE Cabrio, needs some TLC
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7,279 Posts
note all the vacuum lines under teh hood are color coded, that one looks black-white, which is Sb-W in Mercedes speak. There's a vacuum diagram under the hood for all smog related stuff on all USA cars, look for the Sb-W line to see what it is, and where both ends should be connected.
 

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95" W124/ E220 MasterPiece and 01" W210/ E200 KOMPRESSER
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274 Posts
Given from your car responses to you, I guess the most possible culprit would be Item 152+158..
This hose connects the throttle body housing with the regeneration valve...
You could play around the opposite side at the regeneration valve (behind ABS pump).....to see if the hose moves as well.
2643443
 

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1990 Benz 300E 2.6 (mine) ; 1994 E320 Wagon (wife's) ; 1993 300CE Cabrio, needs some TLC
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7,279 Posts
this is the vacuum diagram from my 1993 3.2L California model...

 

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1990 Benz 300E 2.6 (mine) ; 1994 E320 Wagon (wife's) ; 1993 300CE Cabrio, needs some TLC
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7,279 Posts
btw, note the numbers show E28/E32 so valid for 2.8 or 3.2 engines, and code 494 is US Model, code 803 is MY 1993, so near as I can tell, there's nothing California specific on there. I don't see any option codes on my car's datacard that indicate california specific, so I have to presume all 1993 US model M104 HFM cars have EGR ?
 

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1993 MB 300E 2.8
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9 Posts
Discussion Starter #10
Thanks a lot for the tips everyone, I'll try to route the vacuum line correctly and see if that remedies it :)
 

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1993 MB 300E 2.8
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Discussion Starter #11
btw, note the numbers show E28/E32 so valid for 2.8 or 3.2 engines, and code 494 is US Model, code 803 is MY 1993, so near as I can tell, there's nothing California specific on there. I don't see any option codes on my car's datacard that indicate california specific, so I have to presume all 1993 US model M104 HFM cars have EGR ?
[/QUOTE
note all the vacuum lines under teh hood are color coded, that one looks black-white, which is Sb-W in Mercedes speak. There's a vacuum diagram under the hood for all smog related stuff on all USA cars, look for the Sb-W line to see what it is, and where both ends should be connected.

On my vacuum diagram under the hood there is no Sb-W line, but I believe the dashed line going from 3.31 the intake manifold, top is the line in question.
note all the vacuum lines under teh hood are color coded, that one looks black-white, which is Sb-W in Mercedes speak. There's a vacuum diagram under the hood for all smog related stuff on all USA cars, look for the Sb-W line to see what it is, and where both ends should be connected.

On my vacuum diagram under the hood there is no Sb-W line, but I believe the dashed line going from 3.31 the intake manifold, top is the line in question. I'm just not sure where it should go to
2643498
 

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1990 Benz 300E 2.6 (mine) ; 1994 E320 Wagon (wife's) ; 1993 300CE Cabrio, needs some TLC
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7,279 Posts
I believe that purge valve, 12.21 on the vacuum diagram, is down behind the ABS module. per the M104 wiring diagram, it has a brown-green and a black-red wire going to it, and on the wiring diagrams its Y58/1. they look something like a relay, but with only two wires and two vacuum fittings.

I think this is it here, where the screwdriver points and red circle are..

 

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1993 MB 300E 2.8
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Discussion Starter #16
I believe that purge valve, 12.21 on the vacuum diagram, is down behind the ABS module. per the M104 wiring diagram, it has a brown-green and a black-red wire going to it, and on the wiring diagrams its Y58/1. they look something like a relay, but with only two wires and two vacuum fittings.

I think this is it here, where the screwdriver points and red circle are..


Hmm, the vacuum lines on mine are all currently connecting at this part. The vacuum line is currently routed more towards the underside of the car and transmission. I'll try to get some better pictures
 

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1993 MB 300E 2.8
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Discussion Starter #17
Hmm, the vacuum lines on mine are all currently connecting at this part. The vacuum line is currently routed more towards the underside of the car and transmission. I'll try to get some better pictures
Since the line was already through a holder down near the transmission, I assume this end should go somewhere closer to the underside and transmission
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2643714
 

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1990 Benz 300E 2.6 (mine) ; 1994 E320 Wagon (wife's) ; 1993 300CE Cabrio, needs some TLC
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7,279 Posts
Ok, there is a vacuum line to the side of the transmission, this isn't part of the emissions so it's not shown on that diagram. It comes from another vacuum valve, and delays upshifts when the engine is cold, so the cat heats faster. I think that control valve is near the brake booster, actually behind it. I'm on my phone so I don't have access to my docs and diagrams, and I'm not going out there with a flashlight to look at my 93...
 

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1990 Benz 300E 2.6 (mine) ; 1994 E320 Wagon (wife's) ; 1993 300CE Cabrio, needs some TLC
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7,279 Posts
The charcoal cannister is inside the left fender, aft of the wheel well liner.
 

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1993 MB 300E 2.8
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Discussion Starter #20
The charcoal cannister is inside the left fender, aft of the wheel well liner.
Ok, there is a vacuum line to the side of the transmission, this isn't part of the emissions so it's not shown on that diagram. It comes from another vacuum valve, and delays upshifts when the engine is cold, so the cat heats faster. I think that control valve is near the brake booster, actually behind it. I'm on my phone so I don't have access to my docs and diagrams, and I'm not going out there with a flashlight to look at my 93...
Thanks very much for the help :)
I'll take a look and see if I can route it properly based on that tomorrow
 
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