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1999 Tacoma 3.4l Idle issue

Discussion in 'Technical Chat' started by 8982tacoma, Mar 24, 2010.

  1. Mar 24, 2010 at 11:23 AM
    #1
    8982tacoma

    8982tacoma [OP] New Member

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    Jackson, Ms.
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    I have 1999 Tacoma with 3.4l Auto trans with idle issue. I have replace Plugs, wires(the three of them), cleaned throttle body, changed air filter, replaced Idle Air Control valve(had trash in it), checked for vacuum leaks,etc. and still cannot get it to idle below 2100-2200 rpms. Truck runs great other than it will not idle down. I got it to idle down to 1100 rpms last Saturday after adjust idle screw and checking for loose vacuuum lines,etc. Two days later idle is back up to 2100-2200 rpms.
    Anyone got any ideas where to start with this issue. I've never run into anything quite like this before. Thanks in advance for help.
    Ronnie
     
  2. Apr 6, 2010 at 2:20 PM
    #2
    8982tacoma

    8982tacoma [OP] New Member

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    Wow, posted this almost two weeks ago and still no response. Any techs out there with ideas on what direction to go on this? Thanks in advance for any help.
    Ronnie
     
  3. Feb 26, 2013 at 5:41 PM
    #3
    mltitlntd

    mltitlntd Active Member

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    Steven
    New Orleans, La
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    None
    except that the problem with mine is that the engine idles rough, stumbling and sometimes even stalling. I'm going to check the IACV tomorrow. One person told me to check the EGR valve, but I don't think we have one on the 3.4
     
  4. Feb 27, 2013 at 7:10 PM
    #4
    Vstrom30

    Vstrom30 Well-Known Member

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    Have you checked the throttle opener mechanism? It is the small round dash-pot looking part on the throttle body with a vacuum line leading to it. It may have a broken diaphragm, which could cause the rod to extend and bump up the idle. See if it is extended and pushing the throttle open. Then try disconnecting the rubber vacuum hose and then connecting it to a vacuum gun to see if you can get it to retract. Basically, if you were to pinch off or plug this vacuum line to the throttle opener, the idle should raise up to anywhere between 900 and 2000 rpm which could be right on par with your complaint. I don't think this is sold separately from the throttle body, so if it is broken, you will need to visit a junk yard or buy a new throttle body.
     
  5. Feb 27, 2013 at 7:14 PM
    #5
    Vstrom30

    Vstrom30 Well-Known Member

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    You do have an EGR, and it can cause this issue if it is sticking open.

    I didn't realize this thread was so old. :D
     
  6. Feb 28, 2013 at 10:08 AM
    #6
    mltitlntd

    mltitlntd Active Member

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    Guess I resurrected it :) gotta find that EGR valve. So many places for a vacuum leak....
     
  7. Feb 28, 2013 at 7:42 PM
    #7
    Vstrom30

    Vstrom30 Well-Known Member

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    Vacuum is required to open the valve. If your EGR is the culprit, it will most likely be sticking open. A vacuum leak for this mechanism would likely cause it to not work at all, and you should be getting a code for EGR insufficient flow because the EGR temp sensor will not see an increase. Also, if it is constantly stuck open, you can get an excessive flow code. If it just sticks open for short periods and causes the truck to sputter, it may not be long enough for the ecm to set a code.
     
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