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Changed alternator. High start idle won't fall

Discussion in '1st Gen. Tacomas (1995-2004)' started by 96Taco, Apr 1, 2011.

  1. Apr 1, 2011 at 1:04 PM
    #1
    96Taco

    96Taco [OP] Well-Known Member

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    Recently changed my battery and alternator. However my problem now is that the high idle will not cut back down to normal idle.

    By high start idle I mean when you start the engine and it is cold out, engine revs about 2000rpm i guess? then drops to little under 1000 rpm once its warmed up.

    Does anyone see any part of changing the alternator and battery which could potentially cause this problem?

    I really don't want to take in to stearlership for them to look at it so ANY help would be muchly appreciated :)

    Thanks!
     
  2. Apr 1, 2011 at 8:17 PM
    #2
    Supra TT

    Supra TT Supercharged Lifter

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    So now it does not go back down from 2k rpms? Ground issue?... :confused:
     
  3. Apr 2, 2011 at 12:32 AM
    #3
    96Taco

    96Taco [OP] Well-Known Member

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    No it hangs up there.. Im going to play around tomorrow for a few hours and recheck and wiggle all the wiring.. will have access to a multimeter tomorrow so hopefully that sheds some light on things.
     
  4. Apr 2, 2011 at 3:59 AM
    #4
    Janster

    Janster Old & Forgetful

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    The alternator & battery shouldn't have anything to do with the idle. ????

    Have you checked for any computer codes?

    Have you tried tapping the throttle quick/hard?

    How long have you driven it? or should I say....at what point do you expect the idle to lower itself? Have you driven it long enough to warm up enough?
     
  5. Apr 2, 2011 at 7:30 AM
    #5
    dually

    dually Low and slow

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    No electrical.
    Most likely IAC or vacuum leak.
     
  6. Apr 3, 2011 at 8:09 PM
    #6
    96Taco

    96Taco [OP] Well-Known Member

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    Janster - only had the truck for a few weeks. My idle is about 1700 RPMs (even when warmed up) and I remember it being maybe a touch less than a 1000 before i started playing around under the hood.

    dually - Not electrical? if your battery is pretty flat doesn't your car/truck stay on high idle? Even though my battery is brand new I was wondering if it was something to do with this system which is acting up.

    Will keep trouble shooting. Thanks guys
     
  7. Apr 6, 2011 at 9:09 PM
    #7
    96Taco

    96Taco [OP] Well-Known Member

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    Ok I tried this today and had some success. Each time I did it it fell some. Does this mean sticky accelerator cable?
     
  8. Apr 6, 2011 at 9:18 PM
    #8
    davidpick

    davidpick NWXPDTN

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    sorry, i don't have any advice as far as fixing it, but i thought i'd chime in with some confirmation of your target: you're looking for 750 rpm dead-on when it's warmed up.
     
  9. Apr 6, 2011 at 11:04 PM
    #9
    Janster

    Janster Old & Forgetful

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    Maybe or maybe not. You'd have to check the entire cable system from accelerator cable to engine. Could be 'hanging up' somewhere maybe? And check whatever linkages it attaches to. I've read about cable slop before, but you'd have to do research on that.

    I just remember doing that (accelerator slap) on other vehicles for similar reasons - been YEARS and I never did have to diagnose any further. I have no idea what ever happened.
     
  10. Apr 7, 2011 at 5:55 AM
    #10
    magog45

    magog45 Well-Known Member

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    Did you knock a sensor connector when you changed the alternator, if the computer doesn't know the engine has warmed it will still run at the higher speed.
     
  11. Apr 7, 2011 at 8:09 AM
    #11
    96Taco

    96Taco [OP] Well-Known Member

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    Thanks guys. I got a multimeter yesterday so I can start checking electronic components a little more scientifically. Battery is fully charged. Will check ECT but Im pretty sure its not that. As far as vacuum leaks go Im not sure how to test that. Will do some digging around tacomaworld at work today :D
     
  12. Apr 7, 2011 at 8:41 AM
    #12
    borderbrat

    borderbrat Watching Chris4x4 o.O

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    when you disconect the battery it resets the ecu. My old dodge wouldn't idle after i replaced the battery it would just die. The ecu needed a couple driving cycles to go back to normal.
     
  13. Apr 8, 2011 at 8:16 AM
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    96Taco

    96Taco [OP] Well-Known Member

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    Thanks hopefully this is it. Only thing workin so far is tappin the accelerator..for whatever reason
     
  14. Apr 8, 2011 at 1:34 PM
    #14
    i love tacos

    i love tacos Well-Known Member

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    To check for a vacuum leak, remove the intake tube from throttle body. With engine running place your hand over throttle body to block the air coming in. Your engine will continue to run, albeit poorly, if you have a vacuum leak. Meaning it is pulling air in from another source.
     
  15. Oct 17, 2014 at 5:27 PM
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    33yrsoftoys

    33yrsoftoys Over 40yrs now

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    I'd look at the MAF sensor. Give it a cleaning and see if that helps. I had one go out hitting a road bump. Couldn't believe it. Turns out, that was it. When I replaced it I could see a chip on the inside corner. High idle, wouldn't drop when warm, bump the gas, thought it helped. Same symptoms. IMHO, I'd check it. Hope this helps.
     
  16. Oct 17, 2014 at 11:08 PM
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    Tacowaco

    Tacowaco Well-Known Member

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    The IAC is attached to the throttle body, so if tapping the throttle body affects idle that may be the culprit. It seems alot of people have this high idle issue, earlier I posted my experience fixing it on a '03 Jeep wrangler:

    "I have been having a idle issue with my 4.0l, it would idle between 1300-2000 but usually would hover around 1500. I cleaned the IAC, throttle body and harness connections to the sensors ( MAP, TP, Air temp sensor). I hooked up my ODB and I could see that the TP was sending the correct signal. Then I checked all the vacuum hoses using the carb cleaner method (with the engine running, spray it on all the vacuum hoses and see if the engine rpm change). I still had the issue, after pricing the sensors I decided to just start replacing them since they didn't cost that much, I also opted for Mopar since the chinese ones were getting mixed reviews. I got the IAC for about $50 but nothing changed after I installed it, next was the MAP($65) and that fixed the issue. I also learned a MAF sensor has the air temp sensor built in while a MAP sensor uses an external air temp sensor. The air temp sensor would have been my next item to buy. The only thing I would have done different is to have bought the MAP first, it is usually this guy that fails."
     
  17. Oct 18, 2014 at 8:24 AM
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    Supra TT

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    Holy thread revival batman...
     
  18. Oct 18, 2014 at 9:43 AM
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    Tacowaco

    Tacowaco Well-Known Member

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    I replied to the current thread, didn't realize he had revived a dead zombie! :)
     

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