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1999 Prerunner P0171 code

Discussion in '1st Gen. Tacomas (1995-2004)' started by Generalissimo, Dec 27, 2014.

  1. Dec 27, 2014 at 7:28 PM
    #1
    Generalissimo

    Generalissimo [OP] New Member

    Joined:
    Dec 27, 2014
    Member:
    #145055
    Messages:
    3
    Gender:
    Male
    USA
    Vehicle:
    1999 Prerunner
    I've looked up a lot of the posts on this forum but I get the feeling I'm missing something.

    I have a 99 Tacoma Prerunner I bought used about a year ago. The owner kept this truck immaculate and as of today I only have 93,000 miles on it.

    The dreaded check engine light came on just in time for my emissions test for plates. Took it to a mechanic he said I needed new cat converter. I also replaced upstream and downstream o2 sensors. Drove off and 10 mins later check engine comes back on. I'm like rrrriiight. Take it back in and he has it for a week and can't figure out why the CEL is still coming on.

    So I get on the web read all about Mass Airflow Sensor and the likelihood it is dirty throwing that lean fuel code. I take it off and sure enough, there is a speck of black gunk sitting on the little metal sensor. I get some alcohol and qtips and carefully give it a proper cleaning and reinstall it.

    After resetting the computer by disconnecting the negative battery cable for a min, light goes off. For two days, I drive around-- freeway, stop n go, etc... then I'm looking for a parking space and light comes on!! So I head up to Autozone to get the code read and it's still the p0171. So since I did exhaust and cleaned MAF.. (haven't checked pcv yet but will next) I figure to start looking at fuel system.

    I changed the fuel filter and added a can of seafoam to the fuel tank which the salesman seems convinced cleans injector heads (I'm a little skeptical but willing to try it). The seafoam definitely seems to make the truck run smoother but I was never really idling rough or losing power. In fact, my truck runs just fine.

    So at this point in the game- I guess my question is what should I do next if the light comes back on?? (it hasn't yet- but I just reset the code and took it for a 30 mile drive tonight).

    Any help is much appreciated.
     
  2. Dec 27, 2014 at 8:03 PM
    #2
    Generalissimo

    Generalissimo [OP] New Member

    Joined:
    Dec 27, 2014
    Member:
    #145055
    Messages:
    3
    Gender:
    Male
    USA
    Vehicle:
    1999 Prerunner
    I figured as much on the cat... supposedly the mechanic checked for vacuum leaks and found none (but considering his history who knows). I did visually inspect air filter, housing, intake tube.. and any vacuum lines i could see.

    I'm thinking spark plugs next. I figure at 93k it's ok to troubleshoot this code via scheduled preventative maintenance. I don't mind putting the dough in to things I would do anyhow...

    I'm also kind of curious about a possible faulty injector... I would think that would show in acceleration or power.
     

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