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Engine races on start-up 850 1994

posted by  someone claiming to be Volvo Voter on  Tue Jul 18 05:43 CST 2006 [RELATED]

Hi! I hve a '94 850 wagon with an interesting problem. When I leave my office for the night, my engine races. I turn the key and it revs to 2500 RPMs and stays there for ten, maybe fifteen seconds. It drops back down to 1000 RPMs, stays there for a moment, and then down into idle at ~750. What's weird is that the car only does it when I leave my office, it doesn't do it in the morning and it doesn't do it when it's warmed up. I live in Atlanta where it's very hot and humid, and I thought maybe the heat had something to do with it? Overall, other than the engine racing on start, it runs fine, idles great, accelerates smoothly, no probs in city or highway driving.

Any idea what the cause might be?








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    Engine races on start-up 850 1994

    posted by  someone claiming to be fixit 2003 on  Wed Jul 19 06:31 CST 2006 [RELATED]

    When you first start your engine there's no air flow signal coming from the MAS. The fuel mixture is determined by engine temp/O2 sensor inputs and some canned start programming in the ECU. Once the engine starts and air begins to flow through the MAS then it's signal can also be used to adjust the gas flow. Maybe there's some condensation developing in the MAS that's affecting the output when you first start the car and it takes a little extra air flow the dry of the heated sensor wire. Or maybe the wire is dirty although I believe it's supposed to go through some sort of "extra heat" stage to help burn off any potential deposits. Try reseating the MAS plug. Check your air filter too it may be getting dirty.








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    Engine races on start-up 850 1994

    posted by  MadeInJapan on  Tue Jul 18 13:14 CST 2006
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    last visit: Sat Oct 2 06:34 CST 2010
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    Mine did that too....I think it's normal. I suspect the secondary air pump is pumping out any humidity, etc. in the air intake line...it takes longer when it's been sitting all day and hot. Unless you get a code, and the car otherwise runs fine, I'd ignore it.
    --
    1998 S70 T5 Emarald Green Metallic, 2004 V70 2.5T Ruby Red, Previous Owner of Black '94 850 Turbo Wagon. My cars have been running so well lately they've got me worried.








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      Engine races on start-up 850 1994

      posted by  someone claiming to be Volvo Voter on  Wed Jul 19 05:57 CST 2006 [RELATED]

      Thanks for the response. What you say does make sense. I haven't had my car do it to this extent before, but we've also had a long string of very warm, very humid days with very poor air quality. My biggest concern is that I could be damaging the engine. I realize that the engine oil is more fluid when it's hot of course, but still. It's supposed to cool down some over the weekend, so I will definitely keep an eye out to see if it behaves different on start-up. Thanks!







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