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Fluctuating RPM / Speed when driving 850

posted by  jeff w on  Mon Jun 24 17:28 CST 2002
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last visit: Tue Jul 24 17:32 CST 2001
[RELATED]

I am having an ever increasing problem with my car these days. I was pulling a 435 then a 436 A2 socket code in the past couple of months. I have since reset it and as of today took out both O2 sensors and did the torch/brake cleaner cleaning method. I did notice a difference after doing this to my car (accelleraion is back...and how) but the dipping on the tach and odometer is still there.
Basically i am feeling the engine speed and RPM dip about every 6-8 seconds (like the car is hunting for the correct speed.). The dip is pretty minor (can only see it on the tach when i am under 80 Km/hr but feel it always) but i can feel it on and off constantly. I have further checked the vac elbows tonight and can't seem to find any that are collaposed or soft. Any ideas would be appreciated.
Thanks
Jeff W
1994 855 T5 (fluctuating rpm/speed)
1994 854 T5
PS: Currently i do not have any check engine lights on.







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    Fluctuating RPM / Speed when driving 850

    posted by  Volvospeed on  Mon Jun 24 17:57 CST 2002
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    Is it your AC cycling? If no check your TPS








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      Fluctuating RPM / Speed when driving 850

      posted by  jeff w on  Tue Jun 25 16:14 CST 2002
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      last visit: Tue Jul 24 17:32 CST 2001
      [RELATED]

      I test drove the car again tonight. Funny thing is that i still felt the lag (wether the AC was on or not) but it was much less evident then last night. Wondering how that could be? Only thing that i can think of that was different was the ambient temperature outside (cooler tonight and less humid too). The ECU could not be readjusting since i have now cleaned the O2 sensors, could it? That would be mind boggling if that was the case and i highly doubt it is but i am very curious now.
      Any suggestions would be helpful.
      Thanks
      Jeff








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        Fluctuating RPM / Speed when driving 850

        posted by  Volvospeed on  Wed Jun 26 03:08 CST 2002
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        Disconnect the battery for about an hour and let the fuel adaptives reset








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          Fluctuating RPM / Speed when driving 850

          posted by  jeff w on  Thu Jun 27 17:17 CST 2002
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          last visit: Tue Jul 24 17:32 CST 2001
          [RELATED]

          Funny, the technique that i read about for cleaning the O2 sensor mentioned that i should disconnect the battery for about 10 minutes. I did do that but obviously did not see a difference. Your suggestion of an hour may do the trick. I will try that for sure tomorrow. Do you know if the 10 minutes would not work, just curious now?.
          Thanks for all of your suggestions, it is greatly appreciated.
          Jeff W
          1994 854 T5
          1994 855 T5
          PS: I am going to test the car out more tomorrow, but my wife (who was driving this car the last couple of days) has told me the problem is not longer there. Since i have been informed that the fuel adaptives are developed, on an ongoing basis by the ECU, that maybe a combo of driving and time has cured my prob. I will let you know what i find.








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      Fluctuating RPM / Speed when driving 850

      posted by  jeff w on  Tue Jun 25 01:26 CST 2002
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      last visit: Tue Jul 24 17:32 CST 2001
      [RELATED]

      Good call Volvospeed. I will check that tonight. I definately do not have any charge in my AC system and i beleive that it is still in the on position. That may very well be it.
      If it is not, How do you check the TPS. Is there any specific method and is it easy to get at and out?
      Thanks so much for the insight.
      Jeff







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