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2005 PreRunner V6 Fuel Efficiency

Discussion in '2nd Gen. Tacomas (2005-2015)' started by TParkerTac, Oct 10, 2018.

  1. Oct 10, 2018 at 1:56 PM
    #1
    TParkerTac

    TParkerTac [OP] Member

    Joined:
    Mar 15, 2015
    Member:
    #150927
    Messages:
    8
    Gender:
    Male
    First Name:
    Travis
    Riverside, Ca
    Vehicle:
    Tacoma SR5 PreRunner 4.0 V6
    American Racing Ventura Rims, K&N Air, Firestone Air Lift Helper Springs.....
    Have 100K+ Miles on my V6 PreRunner Taco, my fuel efficiency has been steadily declining for the past 4-5 years, tried different things, cleaning the fuel system - injectors, put JB Shorty Headers and a Magnaflow Exaust System, K&N Cold Air System, New OEM 02 Sensors, MAF, etc., still no change. Bought ACCEL Super Ignition Coils.... ”Big Mistake” THEY ARE JUNK, my MPG fell through the floor to 10 MPG. I decided to Replace original OEM Coils with Brand New OEM Coils ($432 for 6) gained 3 MPG from the 13 MPG, I was already getting, instantly.

    Also, my vehicle was spewing very very heavy smelly emissions on Cold Startups so I read a little about the problems with MPG, Emmisions, etc., and I found that the ECT SENSOR (Engine Coolant Temperature) can be a major culprit in poor Idling, High Emmisions, Black Smoke, etc. I replaced the sensor (BIG PAIN IN THE ASS) and have gained another 2 MPG for a total of 18 MPG overall (Mostly City at or around Sea Level), and it easily gets about 22-23 MPG Freeway, which is not bad for my truck having larger wider tires than the stock tires.....

    If anyone is noticing a big drop in MPG, and has tried to remedy the problem as I did, and still not getting desired results, I narrowed my MPG problems down to the “Ignition Coils and the ECT Sensor”. They made a Huge difference, and even at Cold Startup, the emissions are not nearly as strong smelling, which means the ECT Sensor is working correctly. The original ECT Sensor was extremely corroded which actually insulates the sensor and where it may be functioning properly electronically, it is obviously not accurately sensing the Actual Temperature variences of the Coolant correctly, hence resulting in erroneous values being transmitted to the ECU, putting them out of sync with other emissions systems components like the MAF and O2 Sensors.

    If you have up to 100K Miles on your Taco V6 PreRunner, and are experiencing what I have described, I would seriously consider replacing the Ignition Coils with New OEM Coils (NO AFTERMARKET) and also replace the ECT Sensor with an OEM SENSOR. By the way, the ECT Sensor is back by the Firewall behind the intake manifold and is extremely difficult to reach, you’ll have to remove the bolts from two Wire Harnaess Brackets to reach it with a 19mm Open/Box Wrench, but you may want to pay a mechanic to do it for you if you don’t have the patience I have.....lol.

    Took about 2 hours, had to remove the Air Filter Housing for better access.....
     
    Last edited: Oct 10, 2018
  2. Oct 10, 2018 at 2:13 PM
    #2
    RoastyToastyMan

    RoastyToastyMan Well-Known Member

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    Good info. I wonder if there is a way to test the ECT sensor and ignition coils before replacing?
     
    Last edited: Oct 11, 2018
  3. Oct 11, 2018 at 7:33 AM
    #3
    TParkerTac

    TParkerTac [OP] Member

    Joined:
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    Messages:
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    Gender:
    Male
    First Name:
    Travis
    Riverside, Ca
    Vehicle:
    Tacoma SR5 PreRunner 4.0 V6
    American Racing Ventura Rims, K&N Air, Firestone Air Lift Helper Springs.....
    I’m not sure how it could be tested to be honest. I suppose they could measure voltage output to the old sensor while subjecting it to different temperatures, or maybe they can do it in real time at the dealer at a cost.

    My decision to just replace it was based on High Mileage on my vehicle, Information I read about a failing ECT, and my overall decline in MPG. I do have to say though that the biggest change in MPG came from replacing the Ignition Coils.... I also mentioned the Sensor itself was very corroded when I removed it, which led me to believe the corrosion insulated the sensor causing it to read temperatures inaccurately, just a theory of course, but the proof to me is in the results I’m getting.....

    It was worth the $60 and 2 hours of fighting with it.... I guess the question is, could I have cleaned it with a wire wheel and reinstalled it? Would it have functioned properly? I’ll never know bc I didn’t want to go through with the process a second time. It’s located in a very difficult to reach location.
     
    RoastyToastyMan likes this.
  4. Oct 11, 2018 at 7:49 AM
    #4
    b_r_o

    b_r_o We need to talk about your flair

    Joined:
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    Member:
    #202672
    Messages:
    8,076
    First Name:
    Alex
    WA
    Vehicle:
    2015 DCLB
    I've got 85 k and I get around 18 MPG in the city. I've got no engine mods and 275 e rated tires

    You can bench test the coolant temp sensor by doing a resistance check across the pins. The resistance will vary according to temperature, you can find charts that will show you where the sensor resistance should be, Etc

    The coolant temp is pretty standard information on basically all code readers that display data. Sometimes you can catch the sensor reporting a abnormally high or low reading on Startup
     
  5. Oct 11, 2018 at 8:14 AM
    #5
    RoastyToastyMan

    RoastyToastyMan Well-Known Member

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    I may look in to that. I have a 4x4 which I know will never get the same milage as a prerunner but I still only get around 14mpg. Even though it is mostly city it isn't stop and go. I rarely go above 40 or 2k rpm. Doesn't matter if it is winter or summer. I've checked just about everything else that can contribute to poor mpg but not these two. My truck is a 2010 but only has 42k for miles so I don't want to replace things just for the heck of it and I can't really justify replacing things because of high mileage. Thanks for the info guys
     
    I married my tacoma and b_r_o like this.
  6. Oct 11, 2018 at 2:20 PM
    #6
    TParkerTac

    TParkerTac [OP] Member

    Joined:
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    Member:
    #150927
    Messages:
    8
    Gender:
    Male
    First Name:
    Travis
    Riverside, Ca
    Vehicle:
    Tacoma SR5 PreRunner 4.0 V6
    American Racing Ventura Rims, K&N Air, Firestone Air Lift Helper Springs.....
    My main concern was NOT the High Mileage or Age of my 2005, although it can be a definite factor, it was brought on entirely by a marked drop in MPG..... I don’t justify BLINDLY replacing parts solely based on High Mileage either.....

    Just hope my experience helps anyone facing the same issues I had....

    Baby is running like a Champ now!!
     
  7. Oct 11, 2018 at 2:49 PM
    #7
    lynlan1819

    lynlan1819 Well-Known Member

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    Troy
    Las Vegas
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    2017 Pro/2015 Tacoma
    Lifted
    How true,on these trucks nothing beats Factory parts.
     
  8. Oct 11, 2018 at 2:50 PM
    #8
    lynlan1819

    lynlan1819 Well-Known Member

    Joined:
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    Lifted
    Man that's low miles.
     
  9. Oct 11, 2018 at 4:00 PM
    #9
    jross20

    jross20 Well-Known Member

    Joined:
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    John
    Georgia
    Vehicle:
    2000 4Runner SR5 4x4 | V6 | Auto
    Tundra 5100s F+R, OME 880s+890s, duro bumps, etc
    I've still not dropped back below 20 since one time long ago. I presume you guys all drive much harder than me
    :anonymous:

    Even after finishing the 3" lift I can still get 21 mpg
    :cool:

    So I presume my coils are good? although honestly when I changed out the spark plugs because I didn't know when they have been previously I found them to be extremely worn out... but she drove no different before or after and the fuel economy stayed the same which was pretty good. It seems like the bad plugs didn't matter much
    o_O
     
  10. Nov 1, 2018 at 1:49 PM
    #10
    TParkerTac

    TParkerTac [OP] Member

    Joined:
    Mar 15, 2015
    Member:
    #150927
    Messages:
    8
    Gender:
    Male
    First Name:
    Travis
    Riverside, Ca
    Vehicle:
    Tacoma SR5 PreRunner 4.0 V6
    American Racing Ventura Rims, K&N Air, Firestone Air Lift Helper Springs.....
  11. Nov 1, 2018 at 4:27 PM
    #11
    jross20

    jross20 Well-Known Member

    Joined:
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    Gender:
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    First Name:
    John
    Georgia
    Vehicle:
    2000 4Runner SR5 4x4 | V6 | Auto
    Tundra 5100s F+R, OME 880s+890s, duro bumps, etc
    I think you posted in the wrong thread haha
     

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