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Thread: Revs increase on idle

  1. #1
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    Revs increase on idle

    After a warm up period and when the Isuzu has settled down to run relatively smoothly , when parked at the lights after about 10-20 30 seconds , the engine seems to increase idle speed ever so slightly.
    Is this normal?

    I did tweak the idle screw up a bit some time ago and it certainly idles faster when warm than when cold anyway but this change is after it has warmed up and idling at the lights

  2. #2
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    yes its fairly normal it depends on engine temp,oil pressure fluctuates alot when engine temps fluctuate also noticable on turboed engines and main reason is after touching screws on the pump idling,surging and hunting can occur...if you are worried i would do what i have done and fitted a smiths oil pressure guage with increments (0-110psi) not a guage that says high and low.

  3. #3
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    Thanks CHIEF

  4. #4
    JDNSW's Avatar
    JDNSW is offline RoverLord Silver Subscriber
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    Another effect is that the load on the engine decreases as the battery voltage rises and the charging current decreases. Probably a similar effect as vacuum builds up after stopping as well.

    John
    John

    JDNSW
    1986 110 County 3.9 diesel
    1970 2a 109 2.25 petrol

  5. #5
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    thats a very good point JDNSW... and if your wondering it happens to mine on certain occasions so your not alone if it makes you feel at ease

  6. #6
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    Pretty well normal, mine does it too, I estimate about 100 to 150 rpm or thereabouts

    JC

  7. #7
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    Goodoh , thanks

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