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V6 Acceleration / Power Issue

Discussion in 'Technical Chat' started by Dr.Phil, Dec 18, 2013.

  1. Dec 18, 2013 at 10:19 AM
    #1
    Dr.Phil

    Dr.Phil [OP] Member

    Joined:
    Dec 18, 2013
    Member:
    #118791
    Messages:
    8
    Gender:
    Male
    NE, North Carolina
    Vehicle:
    4WD Tacoma SR5
    BFG AT KO
    I've been an unregistered "lurker" in this forum for years and consider it to be a first rate resource for Toyota Tacoma information.
    This is my first post and I'm hoping that I can get some insight on what the issue with my Tacoma might be.

    Vehicle Info:
    2002 Toyota Tacoma SR5, TRD
    3.4L V6 Engine
    Truck has Factory Alarm & Cruise Control
    No modification done to Truck other than the audio system and K&N Replacement Air Filter.

    Problem:
    When accelerator is depressed, RPM increases to about 2,500 and then it will sputter.
    If throttle is opened all the way, engine will backfire through the intake.
    If fuel return hose is restricted, the problem goes away.

    Relevant History:
    Truck has had check engine light on for quite some time now but runs fine and gets same gas mileage. (19 mpg average)
    Error Codes present prior to new problem arising = P0171 System too Lean (Bank 1)
    Current Error Codes = P1135 Air/Fuel Sensor Heater Circuit Response. (Bank 1 Sensor 1)
    Immediately prior to issue presenting itself, I was troubleshooting and eventually located a cross short between the lighting and brake light circuit.
    This cross short occurred inside of the dual filament bulb inside the tail light cluster.
    (One filament blew and subsequently welded itself to the post of the other filament.)
    The cross short caused the brake lights to come on when the head lights were energized.
    It also caused the instrument lights and the marker lights to become energized when the brake lights were activated.

    Troubleshooting Steps already taken:
    In accordance with Toyota Factory Service Manual DI-242 (Problem Symptoms Table), I started troubleshooting the fuel system by following DI-448.
    While doing so, I noticed that if I pinched the fuel return hose while manipulating the throttle butterfly, the acceleration symptom would go away.
    This led me to believe that the fuel injection system was not getting enough fuel pressure to operate properly.
    Starting with the easiest item to eliminate, I replaced the fuel filter. (No Joy)
    The next logical culprit in my mind was the fuel pressure regulator.
    I needed to replace the valve cover gaskets anyway, so I changed the regulator. (No Joy)
    The only items left in the fuel system were the fuel pump and all the plumbing.
    I replaced the fuel pump and the hoses between the fuel tank & hard lines. (No Joy)

    As most of you know, the service that I have already performed is quite time consuming and has parts that aren’t exactly cheap.
    So, I come to you all with my heart in my hand, hoping that one of you is able to help me resolve my problem.
    My thoughts at this point in time is that I either have a partial obstruction in the fuel system or an electrical / electronic problem that is preventing the fuel pump from putting out the necessary fuel pressure or the ECM from operating properly.
    Since the symptom was not present prior to working on the electrical problem, I’m inclined to lean toward an electrical / electronic issue.
    To take the electrical wiring to the fuel pump out of the equation, I disconnected the power to the fuel pump and connected a “Jump Box” directly to it. (No Joy)
    Since replacing the ECM is quite expensive and also not a returnable part, I want to exhaust all other possibilities prior to going down that road.

    Any thoughts or suggestions are much appreciated.
    Cheers,
    Phil
     
    Last edited: Dec 18, 2013
  2. Dec 19, 2013 at 10:18 AM
    #2
    Dr.Phil

    Dr.Phil [OP] Member

    Joined:
    Dec 18, 2013
    Member:
    #118791
    Messages:
    8
    Gender:
    Male
    NE, North Carolina
    Vehicle:
    4WD Tacoma SR5
    BFG AT KO
    Lots of folks have read this thread so far, but no one has been able to provide any guidance yet.

    My next steps are to hook up a fuel pressure test set to determine if the issue is Fuel Pressure / Volume or Fuel Injection / ECM.
    - If the test set indicates a low fuel pressure condition I will focus on the wiring going to the fuel pump.
    - If the pressure is within limits, I will check for proper fuel volume.
    - If fuel volume is out of limits than I will look for fuel line / hose obstructions.
    - If fuel volume is within limits and fuel pressure is within limits then I will conclude that the ECU is causing the problem by telling the fuel injectors to dispense the incorrect amount of fuel into the intake.
    - If it is determined that the ECU is causing the condition, I will use a multi-meter & O-Scope to test the relevant sensors and replace any sensors that test out of limits. (MAF, FA, and O2 sensors)
    - If error condition still exists, replace ECU.


    Fun Fun Fun...
     
    Last edited: Dec 19, 2013
  3. Dec 20, 2013 at 5:05 AM
    #3
    Dr.Phil

    Dr.Phil [OP] Member

    Joined:
    Dec 18, 2013
    Member:
    #118791
    Messages:
    8
    Gender:
    Male
    NE, North Carolina
    Vehicle:
    4WD Tacoma SR5
    BFG AT KO
    Thanks to a suggestion from Jomoka over at Yotatech...

    I was able to solve the mystery for under 10 dollars and less than 10 minutes labor.
    Mass Airflow Sensor...
    Two screws N' a good dousing with MAS Cleaner and life is good.

    The truck was down for several weeks when I was troubleshooting the electrical short and I forgot that I had "recharged" the K&N filter at the same time that I first started to work on the truck.
    I had started the truck and it ran fine, but I had not driven it while troubleshooting.
    Fast forward, $200+ in parts and 4 solid days of labor and I can't figure out whether to jump for joy or cry.
    Oh well, I needed to change the valve cover gaskets anyway and after 183K, it can't hurt to replace the fuel pump with a nice upgraded Bosch pump.
    Hopefully this post can serve as a reference to some poor soul having a similar problem.


    Have a Merry Christmas everyone!


    Cheers,
    Phil
     
    Last edited: Dec 20, 2013
  4. Jan 3, 2014 at 12:53 PM
    #4
    sir1123

    sir1123 Tacomas FTMFW!!!!

    Joined:
    Nov 15, 2010
    Member:
    #46216
    Messages:
    1,383
    Gender:
    Male
    First Name:
    John
    Charleston
    Vehicle:
    99 SR5 Prerunner, Black,3.4L
    3"Ebaich with 5100 Bilstiens, K&N cai, 5% 3M Tint, Magnaflow 18", Hella 500s with 35w 3000k hid retro, 33x9.5x15 BFG A/T
    Had the same problem today! But only when I was pedal to the metal and around 4200 rpm. So I freaked out when I was on the atl freeway and my truck was pop pop pop and the power was sputtery. Grabbed my can of maf cleaner after reading this thread now it seems to be fine at full throttle. Hopefully it stays this way.
     
  5. Jan 3, 2014 at 12:58 PM
    #5
    richardbui23

    richardbui23 That guy

    Joined:
    Apr 26, 2011
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    Richard
    Arlington Texas
    Vehicle:
    Stacy
    did anybody read this with dr.phils voice in there head or was that just me :anonymous: ?
     
  6. Jan 5, 2014 at 6:54 AM
    #6
    Dr.Phil

    Dr.Phil [OP] Member

    Joined:
    Dec 18, 2013
    Member:
    #118791
    Messages:
    8
    Gender:
    Male
    NE, North Carolina
    Vehicle:
    4WD Tacoma SR5
    BFG AT KO
    LOL!

    I'm glad my ordeal was able to help someone out.
    That was a huge pain in the ass!
     
  7. Jan 5, 2014 at 12:29 PM
    #7
    pegcitytacoma

    pegcitytacoma TRD OFROAD

    Joined:
    Dec 23, 2011
    Member:
    #69295
    Messages:
    54
    Gender:
    Male
    First Name:
    Charlie
    Winnipeg Canada
    Vehicle:
    2013 TRD OFFROAD AC MGM
    At bfg's 265/75/16, color matched leer topper with Thule roof rack
    Wish I had seen this post earlier as I had the same issue with my 03 last year. I had thought it was a bad O2 sensor but took it in to a shop near work and had it looked at and fixed ( cleaned the Mass Air Flow Sensor ) and only charged me $45 to do this which I thought was great as the O2 sensor would have been around $450. I also had a K&N filter and the shop had said that the oil in the filter was most likely the cause.
     

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