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Thread: 500SL runnimg issue (CIS-E)

  1. #1
    Senior Member Jord's Avatar
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    500SL runnimg issue (CIS-E)

    So I have a question for you guys, do the CIS-E engine computers ever go bad? My 500SL is a bit weird. It starts up choppy and will stay choppy for a while, then when I go to drive it once I come off an idle it breaks up for a second or two and then accelerates nice and cruises fine. Previous owner replaced the caps, rotors, and coil packs and turned the fuel up till it black smoked at an idle. When I got it I plugged the vacuum back up to the ezl, replaced a fuel pump with a bad impeller along with the fuel accumulator, and turned the fuel down. It runs waaay better than the first day I got it but it still has the stutter off an idle. If I unplug the cold start injector it makes no change on cold start. If I unplug the eha there is no difference when driving. This is making me wonder if the ecu is dead. Anyone ever come across this issue? I just wanna fix the stutter so potential buyers don't look at the car like it's possessed.



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    Senior Member Jord's Avatar
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    Re: 500SL runnimg issue

    Also, the running condition is ever changing like the weather here. Which means it's not adjusting for it's environment.

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    E500E Guru maw1124's Avatar
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    Re: 500SL runnimg issue

    I have not come across that issue. And to answer your question, I'm told all old MB modules go bad, because of the Frako capacitors they used inside. Generally people rebuild those by changing the capacitors. If you have a computer or high end audio repair shop in your town, they may (MAY) be able to do that for you. General information of Frako capacitors here... http://www.tapeheads.net/showthread.php?t=39785

    However, yours sounds like a vacuum leak somewhere -- small enough to be a nuisance when cold, but once things get warm and/or the air velocity high enough, it's not an issue. That's easier to track down than engine electronics. Sure, electronic capacitors go bad over time. But so do vacuum hoses. I'd start by eliminating any vacuum issue.

    Sorry that's not more needle on the head. GL

    maw

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    Senior Member Jord's Avatar
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    Re: 500SL runnimg issue

    Quote Originally Posted by maw1124 View Post
    I have not come across that issue. And to answer your question, I'm told all old MB modules go bad, because of the Frako capacitors they used inside. Generally people rebuild those by changing the capacitors. If you have a computer or high end audio repair shop in your town, they may (MAY) be able to do that for you. General information of Frako capacitors here... http://www.tapeheads.net/showthread.php?t=39785

    However, yours sounds like a vacuum leak somewhere -- small enough to be a nuisance when cold, but once things get warm and/or the air velocity high enough, it's not an issue. That's easier to track down than engine electronics. Sure, electronic capacitors go bad over time. But so do vacuum hoses. I'd start by eliminating any vacuum issue.

    Sorry that's not more needle on the head. GL

    maw
    I have smoke tested the car and the engine pulls 18lbs of vacuum.

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    E500E Guru maw1124's Avatar
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    Re: 500SL runnimg issue

    Spare module?

    maw

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    Senior Member Jord's Avatar
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    Re: 500SL runnimg issue

    Don't have a spare. Going to check and clean ground and test for power. If it has ground and power and makes no change when unplugged then I'll find a module to swap over.

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    Re: 500SL runnimg issue

    If you unplug the computer, i'm pretty sure it will still run but in a default mode that does not read the 02 sensor. I suspect that you may be having a failing fuel distributor. I had a similar issue in a 560SEC that I bought which would stutter on acceleration, making it a little hairy at intersections. This was in the cash for clunkers era and i picked up a replacement FD at the local pnp which solved the problem.

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    Senior Member Jord's Avatar
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    Re: 500SL runnimg issue (CIS-E)

    Yeah if the engine computer was unplugged the idle would suffer. Someone came by today and bought it.

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    Re: 500SL runnimg issue (CIS-E)

    Quote Originally Posted by Jord View Post
    Yeah if the engine computer was unplugged the idle would suffer. Someone came by today and bought it.
    Someone bought the engine computer? Or did you sell the car and no longer have to worry about this problem?


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    Senior Member Jord's Avatar
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    Re: 500SL runnimg issue (CIS-E)

    Quote Originally Posted by gsxr View Post
    Someone bought the engine computer? Or did you sell the car and no longer have to worry about this problem?

    The latter one. He drove the car and wanted it.

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