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excess idle speed engine runaway at start up V70-XC70 2000

posted by  BiggerJohn on  Sun Sep 12 17:50 CST 2010
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last visit: Mon Sep 13 16:57 CST 2010
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Just removed drive shaft now have a new problem to work on.
When she starts the car the engine speed "runs away". It reved to 4200 before she shut the key off. After several starts with shut off if it tries to over rev. it eventually settles down. Any pointers out there. I see from forum searches that the 2000 appears to be throttle by wire. Are we taking a chance at "Toyota Syndrome" engine runaway while driving ?
Thanks in advance for any advice,
John








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    excess idle speed engine runaway at start up V70-XC70 2000

    posted by  tmannian on  Mon Sep 13 04:47 CST 2010
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    last visit: Sat Sep 20 10:31 CST 2014
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    My 850 had a creeping RPM up to about 3500 when I put a defective MAF in (Pick-n-Pull part) so I'd start with looking at that. Air leak is also possible...


    When you pulled off the driveshaft did you do anything in the bay that would have messed with the hoses or electrical wires? Check the O2 sensor and wire, make sure its not damaged. Is this first start after removing the shaft or was it OK for a little while?








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    excess idle speed engine runaway at start up V70-XC70 2000

    posted by  KlausC on  Mon Sep 13 04:36 CST 2010
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    The normal Volvo ETM failure will put the car in limp mode, just enough throttle to coast to a stop.

    Sounds more like a massive air leak into the intake manifold. It could also be a very dirty throttle body that won't close completely, a leak in the vacuum line for the fuel pressure regulator (or FPR failure), a bad MAF, or anything else that effects the fuel/air ratio.

    Klaus







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      excess idle speed engine runaway at start up V70-XC70 2000

      posted by  BiggerJohn on  Tue Sep 14 12:34 CST 2010
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      last visit: Mon Sep 13 16:57 CST 2010
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      Gentlemen:

      Thanks for the ideas.

      As far as trouble caused by removing prop-shaft she tells me that the idle problems was happening before I pulled the shaft.

      I do not think that it is a "massive" vacuum leak as the idle returns to normal operation after the initial cold start up. The stuck throttle body is looking like the culprit all the time.

      I guess I return to my initial question, (sorry have not looked under the hood it's my daughter's car). Is the throttle body operated by a cable or is it "fly by wire" ? Should I be worrying about unintended acceleration ?

      Thanks in advance,
      John








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        excess idle speed engine runaway at start up V70-XC70 2000

        posted by  KlausC on  Tue Sep 14 17:02 CST 2010
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        last visit: Fri Oct 24 10:15 CST 2014
        [RELATED]

        You have an electronic throttle, no cable starting in 1999. But this is not a Toyota, Volvos have brakes and she can always shift to N if there is a problem.

        If it only happens at cold start, I would clean the throttle body. The ECT is asking for more fuel at initial start because it knows it is a cold engine. Of course, if there is a leaking fuel pressure regulator or anything else that is leaking fuel into the manifold, that would also cause high rpms.

        If the rpms go down after a few seconds after start, like 10-15 seconds of 2500 rpm, then clean the throttle body.

        Klaus






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