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Stumbling between 55-60mph 850 1994

posted by  artdrectr on  Wed Feb 18 19:50 CST 2009
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last visit: Thu Aug 28 22:51 CST 2014
[RELATED]

My 850T wagon has recently begun stumbling intermittently between 55-60mph. This after it has warmed up.
Can feel it stumble slightly when just cruising along on flat hwy at 55 or under load (hill) at 55. Not so much at higher speeds.
Can also sometimes feel it when idling at a stoplight.
Does not seem to happen at lower speeds than 55 even when under load (hill).

There are no engine codes or CEL.
Runs fine when cold. Always accelerates very well without problems. Starts great.

My first thought is dirty fuel injector(s), but it seems they would act up at other speeds too.
I dumped some 'fuel injector cleaner' juice in the tank and it did nothing.
And the fuel filter has been changed recently.

Any thoughts?







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    Stumbling between 55-60mph 850 1994

    posted by  KlausC on  Thu Feb 19 04:55 CST 2009
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    last visit: Fri Oct 24 10:15 CST 2014
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    I hope you are not using platinum spark plugs. Copper plugs are much better.

    Have you checked the codes?
    --
    My name is Klaus and I am a Volvoholic.








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      Stumbling between 55-60mph 850 1994

      posted by  artdrectr on  Thu Feb 19 06:58 CST 2009
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      last visit: Thu Aug 28 22:51 CST 2014
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      No codes or CEL.

      Possible it could be the Throttle Position Sensor (TPS)?

      Also, we are having a lot of wet weather here SF Bay Area, would moisture have anything to do with such a narrow problem?








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        Stumbling between 55-60mph 850 1994

        posted by  KlausC on  Thu Feb 19 07:38 CST 2009
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        last visit: Fri Oct 24 10:15 CST 2014
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        A TPS problem would throw a code. Of couse wet weather would cause problems, specially if the dist cap has a crack or the plug wires are wet. But, both of those items shold dry up after a few minutes of running. Water collecting in the spark plug holes could be a factor if you drive through a lot of puddles.
        --
        My name is Klaus and I am a Volvoholic.








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        Stumbling between 55-60mph 850 1994

        posted by  big Har on  Thu Feb 19 07:34 CST 2009
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        last visit: Mon May 30 19:22 CST 2011
        [RELATED]

        Yes, moisture could be causing problem. Ck dist cap and rotor it old replace.








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          Stumbling between 55-60mph 850 1994

          posted by  artdrectr on  Thu Feb 19 18:28 CST 2009
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          last visit: Thu Aug 28 22:51 CST 2014
          [RELATED]

          Well, I just found the problem.

          I checked the distributor, and the lowest plug wire was free. Sorry for not checking that earlier before posting.
          Looks like the last mechanic to work on it didn't attach the wire all the way (I had some work done on it recently). Gotta say it's a chore to get that lowest one on. But the insulation is charred on the tip so I'll need new wires. We'll see what the mechanic says about replacing the wires.

          No wonder the car ran worse in the rain, you can imagine what the rain did to an open plug wire.

          But mostly, I'm just surprised how well the car ran on only 4 cylinders!!






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