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Thread: litte bit of a rough idle when under elec. load

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    litte bit of a rough idle when under elec. load

    I'm still chasing down my poor mpg issue. I noticed that when I'm at idle and i flip the heat on the engine doesn't idle as smooth, little bit of vibrating in the steering wheel when I'm at a light. It isn't horrible but definitely noticeable. Any thoughts?Thanks.

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    Re: litte bit of a rough idle when under elec. load

    When you say "flip on the heat", do you mean moving the temp control from cold to hot, or turning on the blower?

    Gwen
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    Re: litte bit of a rough idle when under elec. load

    the blower motor. It also seems to happen when I turn on the headlights.Thanks

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    Re: litte bit of a rough idle when under elec. load

    Anytime you induce an electrical load on the system the alternator will start cranking out some juice, putting more load on the engine.
    Not at all uncommon for a "high draw" system (think headlights, heater, rear defroster) to cause the idle to come down a couple of hundred RPM.

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    Administrator llamavan's Avatar
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    Re: litte bit of a rough idle when under elec. load

    What he said.

    How old is your battery? IME, an RPM drop in conjunction with blower motor and/or headlights (or a noticeable drop in headlight brightness when the engine drops to idle) can be a tip-off that the alternator is already busy trying to charge a dodgy battery (or charge via dodgy connections). A constantly-busy alternator is no good for mpg.

    Gwen
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    1989 4WD 5-speed DLX; 410K and an odd sense of humor ("Skylervan")

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