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Thread: Need help... E420 running rough and quiting

  1. #1
    Junior Member Ricardo's Avatar
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    Exclamation Need help... E420 running rough and quiting

    Here is the history of work trying to remedy.. open to all suggestions...

    Ebay buy in 2013, with only 61K, now has around 80K.
    Ran a little rough (very intermittent) when I got it at low speeds but seemed fine on highways. Drove it between Stuart FL, and Charlotte a few times and after some 15Kmi the frequency of the rough running became very regular. I replaced caps/rotors in this timeframe.

    First indy diag seemed to think it was the MAS as a shot of cleaner seemed to bring her back to life..
    So, I decided if it was the MAS lets fix her.
    First repair was MAS, crank sensor and fuel filter, and new ignition module. No difference.
    Did smoke test, no leaks reported.
    Tried a 2nd indy, and we suspected the throttle actuator, so sent to beckman who confirmed it was good. Tried another crank sensor, No improvement...

    Ok so now it seems indy friends are stumped, so since RennTech is in my backyard, I figured they should have some experience with the W124 so I explained the history, what had been done and gave it to them. They quickly turned it around after 9 hours of diagnostics as fixed by swapping two vacuum lines... took it home, drove for a week, (went away for 2) and when I came back, drove it all of 2 miles and rough running returned and would quit. ($900 bill!)

    The car had been left with Renntech for 6 months and they claim they could not duplicate the rough running, so in dec I returned to pick it up. Drove it around the block and rough running shows its face again.. so drove it right back to Renntech.. Their lead technician saw it running rough in their lot so i left it with them.. again. Its now march and I got an email saying they cant duplicate so car should be picked up.
    Will be getting it in the morning 3/2/2017.

    So, I hate to abandon such a beautiful sedan...
    Ideally I might find a well running example and use it as a reference (and perhaps part swapping), but need to find a <new> friend in the Stuart, FL area.. OR.. start throwing parts at it.. OR even considered taking it to West Palm MB since they have been around for a while and may have older tech familiar with the model..

    I have begun considering buying another (working) E420 to help get this one back on the road.. just not ready to make that decision just yet..

    any questions/suggestions? I will be rewarding those who are key to resolving this issue (non monetary rewards )

    thanks in advance
    71' 280SL,
    83' 300TDT, 89' 560SL,
    92' 500E, 94' E420, 95' SL600, 95' E320 Cab (x3)
    12' C300 4Matic

  2. #2
    .036 Hoonigan™
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    Re: Need help... E420 running rough and quiting

    Ricardo, you mention replacing caps/rotors, but not the insulators behind the rotor bracket. This has been popping up on the forum quite often recently. A defective cap is a remote possibility but IME, this tends to be fairly consistent when it happens, not intermittent - I doubt it's the cause of your issues. Just curious, what brand cap/rotor did you install in 2013?

    Anyway: I would remove the cap, rotor, rotor bracket, and insulator - then inspect the back side of the insulator for any sign of liquid. If there is ANY liquid on the back, it may be the cause of your problems. Clean everything bone dry and re-assemble, see if that makes the problem go away for a while. If the back of the insulators is dry and clean, something else may be the cause, and would need further diagnosis.

    Additional reading:

    http://www.500eboard.com/forums/showthread.php?t=9362

    http://www.500eboard.com/forums/showthread.php?t=8457 (note photo in post #11)

    http://www.500eboard.com/forums/showthread.php?t=10825 (post #3 and #7)

    http://www.500eboard.com/forums/showthread.php?t=10710 (post #6 through #21)

    Dave M.
    1997 E420 (Bugeyes)
    1994 E420 (Blondie)
    1994 E500 (Q-ship)
    1992 500E (Mach 5)
    1987 300D (Sportline Stage 2)
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  3. #3
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    Re: Need help... E420 running rough and quiting

    Sorry to hear about your issues. You might buy a code reader and take on some responsibility. These cars are old and most shops don't have experience with them anymore. Renntech might have done M119 6.0 liter conversions, but I bet it was 20 years ago and most of their staff doesn't seen anything more than 10 years old or less.
    In my area, most of the really good independant shops are packed with the newer cars and service. Easier to make lots of $$.


    Read the codes for every pin and then clear them all. It really shouldn't be hard to run to ground? Do you have the correct non-resistor spark plugs in the car? Open the gap up per Klink. Measure all the wires resistances while you have the plug boots pulled. MB's like to be square in the the center of the tolerance range. Just seems that German stuff runs better that way.


    Just some advice- as a owner of 3 cars which are over 25 years old.


    Michael

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  5. #4
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    Re: Need help... E420 running rough and quiting

    you drove right past us! We've had out fair share of rough running 124/m119 equipped cars to deal with.


    Jono
    Blue Ridge Mercedes Jonathan Hodgman
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    08 E63; 05 E55 Estate; 95 S600; 93 500E Brumos/RTech; 92 500E T/R; 93 500E Pearl Gray
    91 560SEC ECE; 87 Hammer Coupe, Sedan and Wagon 6.0L 32V; 86 560SEL AMG 6.0L 32V

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    Re: Need help... E420 running rough and quiting

    Quote Originally Posted by Ricardo View Post
    ...took it home, drove for a week, (went away for 2 weeks) and when I came back, drove it all of 2 miles and rough running returned and would quit. ($900 bill!)
    FYI. The sentence above is a big red flag for me, pointing at the liquid-on-insulators syndrome. As mentioned in the other threads, on my car it would run fine if driven frequently. But if parked 2+ weeks the misfire+stalling would return. I was able to consistently reproduce this by parking the car for at least 2 weeks. Replacing the insulators (which had liquid on the back) permanently cured the issue. I can park it for 2 months now and it runs perfectly after sitting that long.

    Might be something else entirely, but this would be #1 at the top of the list to check.


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  9. #6
    Junior Member Ricardo's Avatar
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    Re: Need help... E420 running rough and quiting

    Wont be with the car for a few weeks, but I will take a look see as soon as I can.
    I did not replace the insulators behind the bracket..
    I used OEM MB cap & rotor (MB Northlake dealer, plug for MBCA members get 25% off).

    Additional information as I think more about it (been a while since I had the car..)
    - Typically when the rough running begins.. its just a matter of time before she cuts out.. At this point it would seem that the car needs to cool down before she will start again.
    - Thinking about it last night, one thing that has not been done is a new set of wires (so the wires are the ones that came from her ebay home). I plan to pickup a set and new plugs so as to eliminate that variable.


    Will report back later in march when I get some time to dedicate to her.
    71' 280SL,
    83' 300TDT, 89' 560SL,
    92' 500E, 94' E420, 95' SL600, 95' E320 Cab (x3)
    12' C300 4Matic

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    TerryA (04-08-2017)

  11. #7
    Junior Member Ricardo's Avatar
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    Re: Need help... E420 running rough and quiting

    Agree.. I have been thinking about getting a reader for a while now..
    No lights are triggered by any of the rough running behavior, and if memory servers (50% confidence here ) codes were read a few times and there werent any.
    I will pickup a reader and familiarize myself with some of the code tables in the interim until I get the chance to dedicate a few hours to the diagnosis..

    As mentioned with above reply.. plan to put new wires and plugs on her.. to eliminate those variables, and inspect behind the insulators..

    thanks for taking the time for suggestions..
    will report back in a few weeks (taking motorcycle trip northward for some colder nights
    71' 280SL,
    83' 300TDT, 89' 560SL,
    92' 500E, 94' E420, 95' SL600, 95' E320 Cab (x3)
    12' C300 4Matic

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    TerryA (04-08-2017)

  13. #8

    Re: Need help... E420 running rough and quiting

    Question. after one replaces ignition components, does the car go thru a re-adaption process?

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    TerryA (04-08-2017)

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    Re: Need help... E420 running rough and quiting

    Forgot to mention: the liquid-on-insulators syndrome does not generate any DTC / error codes, or warning lights on the dash.

    After replacing ignition components, the LH will adapt as necessary, but I doubt it would change adaptation much unless the old ignition components were in bad enough condition to affect combustion efficiency (not likely, but possible).


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  17. #10
    E420 Guru Ascension's Avatar
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    Re: Need help... E420 running rough and quiting

    Quote Originally Posted by Ricardo View Post
    Wont be with the car for a few weeks, but I will take a look see as soon as I can.
    I did not replace the insulators behind the bracket..
    I used OEM MB cap & rotor (MB Northlake dealer, plug for MBCA members get 25% off).

    Additional information as I think more about it (been a while since I had the car..)
    - Typically when the rough running begins.. its just a matter of time before she cuts out.. At this point it would seem that the car needs to cool down before she will start again.
    - Thinking about it last night, one thing that has not been done is a new set of wires (so the wires are the ones that came from her ebay home). I plan to pickup a set and new plugs so as to eliminate that variable.


    Will report back later in march when I get some time to dedicate to her.
    You are describing exactly the symptoms I had with my 95 E420. Cranks and runs ok when cold but pitched a fit when it got hot never quit but if shut down would not restart until it cooled. Would back fire and just spin on the restart until it cooled then would run normally until it got hot again. Caps and rotors looked ok and we ran in circles with the car. Replaced the caps rotors pulled the insulators and while they looked fine from the front both were wet on the back with a weird jell.

    Cleaned the insulators and sprayed them with a water proof coating and the problem never returned.
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    Last edited by Ascension; 03-10-2017 at 09:21 AM.
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  19. #11
    Junior Member Ricardo's Avatar
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    Re: Need help... E420 running rough and quiting

    So an update... While I was traveling, I left it with the local indy.
    Good news for the car, not so much for the wallet. Some more detailed diags revealed that the SLIDE (throttle actuator) was the culprit. It would seem that once warmed up the circuit board would short the one or more of the components.
    After confirming the correct part with our buddy at the MB Classic center (who offered the not inexpensive part at wholesale to me) I opened the wallet.
    She seems to be running well now with no symptoms of the issue.. Driving now cautiously (no fun getting stuck) but positive so far .

    Thanks as always for the help and educational tips..

    Ricardo
    71' 280SL,
    83' 300TDT, 89' 560SL,
    92' 500E, 94' E420, 95' SL600, 95' E320 Cab (x3)
    12' C300 4Matic

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  21. #12
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    Re: Need help... E420 running rough and quiting

    a factory ETA? Phew, I don't even want to know!

    Not shocked though, we replace a LOT of ETA's these days, both early and late build dates.

    Jono
    Blue Ridge Mercedes Jonathan Hodgman
    Mercedes Repair Atlanta
    http://www.blueridgemb.com/
    08 E63; 05 E55 Estate; 95 S600; 93 500E Brumos/RTech; 92 500E T/R; 93 500E Pearl Gray
    91 560SEC ECE; 87 Hammer Coupe, Sedan and Wagon 6.0L 32V; 86 560SEL AMG 6.0L 32V

  22. #13
    Junior Member Ricardo's Avatar
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    Re: Need help... E420 running rough and quiting

    Its no secret.. MB Classic center price offered was $1740. Could have had a reman one for range of 800-900 but was concerned if their testing wasnt under heat it may not have revealed the issue and was concerned reman that wasnt tested under heat could have other possible "about to go" components.. so bit the bullet for the OEM one.. with the low miles, hoping to be driving her for a while
    71' 280SL,
    83' 300TDT, 89' 560SL,
    92' 500E, 94' E420, 95' SL600, 95' E320 Cab (x3)
    12' C300 4Matic

  23. #14
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    Re: Need help... E420 running rough and quiting

    Quote Originally Posted by Ricardo View Post
    Its no secret.. MB Classic center price offered was $1740. Could have had a reman one for range of 800-900 but was concerned if their testing wasnt under heat it may not have revealed the issue and was concerned reman that wasnt tested under heat could have other possible "about to go" components.. so bit the bullet for the OEM one.. with the low miles, hoping to be driving her for a while
    BBA doesn't test under heat, but Beckmann does, they get installed and driven on before being sent.. Better then any stationary test rig

    J
    Blue Ridge Mercedes Jonathan Hodgman
    Mercedes Repair Atlanta
    http://www.blueridgemb.com/
    08 E63; 05 E55 Estate; 95 S600; 93 500E Brumos/RTech; 92 500E T/R; 93 500E Pearl Gray
    91 560SEC ECE; 87 Hammer Coupe, Sedan and Wagon 6.0L 32V; 86 560SEL AMG 6.0L 32V

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