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2001 tacoma backfire out of the air box

Discussion in '1st Gen. Tacomas (1995-2004)' started by archy32, Feb 15, 2012.

  1. Mar 7, 2012 at 7:13 PM
    #21
    hayabusa3303

    hayabusa3303 Well-Known Member

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    Idle control valve is screwed up making it run rich. ( had this happen before to mine)

    Or your TPS is out of wack.
     
  2. Mar 7, 2012 at 7:23 PM
    #22
    crainholio

    crainholio Well-Known Member

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    In many vehicle powertrain control systems I've worked on, 4K RPM is the transition from Mass Air Flow input to static Volumetric Efficiency table lookup for fueling. Don't know if Toyota/Denso use this breakpoint but it seems likely given your symptoms.

    MAF actually reads the air quantity being fed to the engine, whereas the VE table values are static integers based on calculations from the factory...much less accommodating of glitches even in a closed-loop oxygen sensor fuel management system.

    If you can get access to a scanner, get readings on Long Term Fuel Trims for Bank 1 and Bank 2 at various RPM/load combinations and report back. Get idle, steady cruise, uphill in a high gear, hard but not WOT acceleration through the gears, and holding at 4K RPM while the backfire happens. Report your numbers.

    1.) Check to see if the LTFT numbers vary much between the two banks, there should be no more than around 5% difference between them at any given time.

    2.) Check to see if they're ever > 10% or < -10%, even if they're closely matched between the two banks.

    Post your data and let us know what you find.
     
  3. Mar 15, 2012 at 6:19 AM
    #23
    98tacoma27

    98tacoma27 is going full "SANDWICH" Moderator

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    Some stuff. Not a lot, just some.
    There is no EGR on a 3.4
     
  4. Mar 20, 2012 at 8:55 AM
    #24
    archy32

    archy32 [OP] Member

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    Ive checked everything but the ECM. I guess Ill have to buy one
     
  5. Mar 20, 2012 at 9:13 AM
    #25
    skytower

    skytower Well-Known Member

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    Hitch and wiring, aux back-up light, rear strobe lights, radio and underseat sub.
    How often do you run seafoam through your engine?
    Build ups of deposits can increase compression and cause pre-ignition problems. Running rich can have the same effect, but can be found with a smog test.

    Please list the tests you have accomplished and the results. Saying you have checked everything but the ECM isn't going to help us give you any more constructive ideas.
     
  6. Mar 20, 2012 at 9:16 AM
    #26
    meatman

    meatman I deal with dead animals

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    My 01 would occasionaly do this but it was at lower speeds and felt like the cat was stopped up. I was'nt getting any codes either but went ahead and changed the o2 sensors out. This seamed to fix my problem but i dont know if it was the sensors or that when i changed the downstream one the gasket was completly rusted away. It might be somethig to look at
     
  7. Mar 22, 2012 at 8:47 AM
    #27
    archy32

    archy32 [OP] Member

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    checked the timing. Check the idle control. Changed plugs and wires. Tested all the sensors. disconnected all controls and everyone gets the code when i unplug them. Plug them back in code turns off. Checked all the injectors. This is the only reason I believe it could be the ECM.
     
  8. Mar 22, 2012 at 8:48 AM
    #28
    archy32

    archy32 [OP] Member

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    Also replaced the fuel filter. I have not run any cleaners or boosters in it for awhile
     
  9. Mar 22, 2012 at 10:27 AM
    #29
    skytower

    skytower Well-Known Member

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    Hitch and wiring, aux back-up light, rear strobe lights, radio and underseat sub.
    An exhaust gas analysis will tell you if it is running too rich. Not sure if you have a smog test in your area, but a shop that does work for that will have one.
    A vacuum test will show overall engine health, but will not show a floating/sticking valve at speed. It's worth doing, and a vac gauge is cheap.
    A leakdown test gives more detailed info than a compression or vac test. It will tell you which cylinder has a problem. An inexpensive tester can be found here:
    Work from the cheap to the expensive. Prove the ECM bad before you condemn it. That way you won't have a pile of used, working spares. That is a very expensive way to troubleshoot.

    Let us know what you find. Happy hunting!
     
  10. Mar 22, 2012 at 10:30 AM
    #30
    skytower

    skytower Well-Known Member

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    Hitch and wiring, aux back-up light, rear strobe lights, radio and underseat sub.
    Oh yea, I forgot... Seafoam! Seafoam! Seafoam! :D
     
  11. Mar 27, 2012 at 2:35 PM
    #31
    archy32

    archy32 [OP] Member

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    OK so here it is guys. The half moon that keeps the crank shaft and the pulley spinning as a unit gave out. This eventually caused the bolt that holds the pulley to come loose.This was causing the pulley to float out a bit and cause an issue with timing. So. Took it apart, replaced the half moon, and put it back together. GOT IT!!:D The truck is back to normal. Thanks to everyone who tried to help.
     
  12. Mar 27, 2012 at 2:36 PM
    #32
    archy32

    archy32 [OP] Member

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    Yes Iroh. Even you
     

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