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p0420 code, heavy exhaust smell, bad mpg, rough idle

Discussion in '1st Gen. Tacomas (1995-2004)' started by x2468, Jan 22, 2017.

  1. Jan 22, 2017 at 4:36 PM
    #1
    x2468

    x2468 [OP] Well-Known Member

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    Doing some research on the P0420 code. Seems like it could be one of the o2 sensors on the exhaust, could be the exhaust itself, could be a bad fuel pump? Where should I start first?
     
  2. Jan 22, 2017 at 4:38 PM
    #2
    My02SC

    My02SC instigator

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  3. Jan 22, 2017 at 5:08 PM
    #3
    CroTaco

    CroTaco Well-Known Member

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    Take it in and have a diagnostic done.
     
  4. Jan 22, 2017 at 10:15 PM
    #4
    cruiserguy

    cruiserguy Well-Known Member

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    Nah, don't do this OP.
     
  5. Jan 22, 2017 at 10:31 PM
    #5
    cruiserguy

    cruiserguy Well-Known Member

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  6. Jan 22, 2017 at 11:05 PM
    #6
    Caligula

    Caligula It's the COVFEFE

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  7. Jan 22, 2017 at 11:06 PM
    #7
    jbrandt

    jbrandt ......LOADING

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    Replace whatever is cheapest first.
     
  8. Jan 23, 2017 at 3:51 AM
    #8
    Indy

    Indy Master of all I survey.

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    Throw away enough cheap money and is not cheap anymore.


    All the downstream sensor does is check how the cat is functioning. It doesnt control anything ahead of it, just tells you the is an issue somewhere upstream. If i have a hole in my leg j don't go buy new socks because they're cheap and mine feel wet.
     
    My02SC likes this.
  9. Jan 23, 2017 at 5:16 AM
    #9
    ghs57

    ghs57 Well-Known Member

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    FSM says: 1-Check for exhaust leak, 2-Check A/F sensor (bank 1, sensor1), 3-Check oxygen sensor (bank1, sensor 2), 4-Replace 3-way cat. There is a diagnostic procedure if you have a scan tool with freeze frame data.

    I have had this code, but usually with other codes. Have had exhaust leak, and bad sensors. Haven't has to replace the cat yet (160K).
     
  10. Jan 23, 2017 at 6:47 AM
    #10
    Sandman614

    Sandman614 Snarky TWSS elf, Travis #hotsavannahdotcom, LRGRNR

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    Diagnose the problem and then correct the problem..
    Check your fuel pressure and then go from there.
     
  11. Jan 23, 2017 at 9:16 AM
    #11
    jbrandt

    jbrandt ......LOADING

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    Well obviously, yes.

    Many times however, there are several possibilities for a given symptom. If you've got a $10 part that's easy to replace that could be the problem, might as well throw it on there and see if it fixes it.

    I'd rather that then going straight to the $600 solution first only to find out that's not the problem.
     
  12. Jan 23, 2017 at 10:35 AM
    #12
    Sandman614

    Sandman614 Snarky TWSS elf, Travis #hotsavannahdotcom, LRGRNR

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    Or do the proper diagnostic, checking fuel pressure, exhaust leaks, o2 resistance/heater voltage, etc, and replace the correct part.
     
  13. Jan 23, 2017 at 10:46 AM
    #13
    jbrandt

    jbrandt ......LOADING

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    I don't disagree.

    But most post people don't have all the equipment/tools/mechanical know how to check all that stuff "properly", which is probably why they're on the internet asking for advice.

    You work with what you have. You have to weigh the cost/benefit of doing those detailed tests, too. How long does it take to test it vs. how much does the diagnostic tool cost vs. just replacing a part that could probably stand being replaced anyway.

    If there's a good chance the problem is a $10 part, what's the bfd in replacing it? Hell, many shops I've seen will do that, too.
     
  14. Jan 23, 2017 at 11:17 AM
    #14
    Sandman614

    Sandman614 Snarky TWSS elf, Travis #hotsavannahdotcom, LRGRNR

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    I would rather give correct advise and offer my tools and workspace to help someone correct a problem than give them advise on a half-ass fix. The BFD is that a lot of times replacing an o2 sensor is just masking the true problem. Lots of shops will do that because they are shady and want you to come back, and know you will.
     
  15. Jan 23, 2017 at 11:20 AM
    #15
    Sandman614

    Sandman614 Snarky TWSS elf, Travis #hotsavannahdotcom, LRGRNR

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    Check for exhaust leaks, check on youtube for various methods. Get yourself a Fuel pressure gauge with the correct fittings to check the fuel pressure on your vehicles. If that's not feasible for you check with your local TW guys, someone probably has the tools and is willing to help you out.
     
  16. Jan 23, 2017 at 1:38 PM
    #16
    cruiserguy

    cruiserguy Well-Known Member

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    Another thing to keep in mind is that the O2 sensor and A/F sensor are actual wear items. I don't recall off the top of my head, but I think Mr. T says to replace them every 100k. If these haven't been replaced, most likely with your mileage (not sure what you're at on the odometer) they should be replaced. So it's not a bad idea to replace them. If you haven't already done them, you wouldn't just be throwing money at your truck and hoping for a fix.
     
  17. Jan 23, 2017 at 9:18 PM
    #17
    LifeOverTheEdge

    LifeOverTheEdge Well-Known Member

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    A whole lot
    Mine wound up being an exhaust leak, where the headers meet the 1st cat.
    I found that out AFTER I bought new cats and O2 sensors and god knows what else to fix this problem, lol.
    Check for any leaks first...please.
     
  18. Jan 23, 2017 at 10:18 PM
    #18
    mechanicjon

    mechanicjon They call me "Jonny Stubs"

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    I've seen egr valves slightly stuck open cause similiar issues.
     
  19. Jan 24, 2017 at 7:47 AM
    #19
    CroTaco

    CroTaco Well-Known Member

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    Options: throw parts at it and hope something sticks, spend a ton of money.

    Or...

    Pay 89.99 for a diagnostic and get it right the first time. And spend less money
     
  20. Jan 24, 2017 at 7:49 AM
    #20
    mechanicjon

    mechanicjon They call me "Jonny Stubs"

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    You have faith in the 89.99 diag fee?
     
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