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  1. #1
    Zeltar
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    '97 540i missing/shuddering

    I've got a '97 540i auto with 204k miles that's recently started exhibiting the followng symptoms:

    On light throttle or at constant speed under load (uphill, AC on, etc), I'm getting intermittent 'missing' - it's hard to describe, but it's as if it misfires on several cylinders sequentially with the result of a half second or so loss of power that causes sort of a jerk sensation, then a surge as power resumes. If you happen to be looking at the tach when it happens, you can see the RPM drop and then recover. It doesn't happen at idle or under heavy throttle.

    The timing of this seems to be totally random - it might do it three or four times in a ten second period, or once every few minutes, or whatever. Sometimes it goes away for weeks at a time. Every now and then, it will get worse for a few seconds to the point where it's hard to accelerate at all, like it's misfiring more than it's firing. Applying heavy throttle makes this condition go away.

    Odd thing is, the MIL has not illuminated, and no codes appear to have been recorded - based on past experience working on this car, I'd think it couldn't misfire like that without something coming up, codewise.

    Any thoughts? I've been thinking about fuel starvation/contamination issues (the problem started less than an hour after I nearly ran out of gas out in the country and had to fill with low-octane gas from a little one-pump station), or maybe something MAF related, but my understanding is it would be hard to have either of those problems without tripping some sort of OBD threshold.

    Thanks in advance for any help you can offer.


  2. #2
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    Member No: 4328 jimlev will become famous soon enough jimlev will become famous soon enough jimlev's Avatar
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    The first things that come to mind are (m)

    Have you checked to make sure there is no oil in the plug wells? Take a look at the sparkplugs, especially if they have more than 60K on them.
    Look at all of the air intake tubing from the MAF to the intake manifold.
    When was the last time you changed your fuel filter, possibly it is getting plugged. Generally when it starts to get plugged the engine will run OK at idle but as the load increases (highway speeds) it will start to miss because of fuel starvation.
    Fuel pump is another possibility.

  3. #3
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    Member No: 21320 edjack will become famous soon enough edjack's Avatar
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    ... or, check for Pending Codes. The cam >>

    position sensor may be intermittent. If it is, there will be a code pointing to the CPS circuit. That's how mine failed.
    Ed in San Jose. BMW CCA member since 1987 (Nr. 62319). Golden Gate Chapter. '97 540i 6 speed. Build Date 3/97. Aspensilber over Aubergine leather.

  4. #4
    Zeltar
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    Update: Looks like a transmission issue

    Just a little while ago the CEL came on. I pulled the code and it was p0740, "Torque Converter Clutch Circuit Malfunction", so this may not be an ignition/fuel supply issue at all. Helps to explain why I wasn't seeing any of the codes I'd expect for those things.

    Thanks for everyone's help.

  5. #5
    PAnos
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    Do a search for that code "p0740" I seem >>

    to remember someone talking about having to change the torque converter. Probably lots of labor, unfortunately.

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