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Wierd problem with my 5VZFE.

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  • Wierd problem with my 5VZFE.

    Hello all,

    I have decided to ask a prado forum on thoughts about my issues with my prado.
    i have just joined so i apologise if i have posted this wrong.

    I own a 2000 Vzj95 prado 3400 v6 GXL.
    I bought it 2 years ago with a missfire that i couldnt put to my knowledge as a head gasket issue, thinking it would be coils or something... got it cheap.
    I am not new to cars and have good knowledge regarding diagnostics. But this baffles me.
    i have done a lot of work to it in this time, new suspension, rack, mounts, full major included the trans and diffs, new rad, new hoses, water pump, timing belt etc... basically gone right through the 4wd as i want it for trips and being at 395ks i knew most of it would be stuffed... i replace all 3 coils with new genuine ones, new leads and plugs... the missfire continues...
    Fuel filter is done and all...
    it still rough idles and yet drives fine under load... pops in the exhaust at idle like its missing a cylinder or its open.

    year later, its now worse... but only suddenly, now i find its progressively worse after its first run. From cold its ok but rough and after it reaches temp its still fine.... park somewhere and come back and i get 5 cylinders...
    Sometimes it comes good whilst driving and sometimes not.
    I have TK tested it, no combustion read. It doesnt use coolant or overheat and the oil is clean.
    I have heard it could be a valve riding? But it changes too often and between to be something that should be stuck open?

    Also i notice it really plays up when i use the aircon.

    the plugs read fine too.

    i just am trying to avoid pulling it apart and rebuilding it and wasting time and money

    i was leaning on an old cam sensor?
    obviously its not crank as it runs.
    it does take a few cranks to start though.

    compression test is basically 140s across all banks dead cold.

    any help would be great, i wonder if anyone else has had this issue?

  • #2
    With nearly 400,000 kms on the clock I would be pulling the injectors and getting them cleaned and tested. Not a big job, just remove the plenum chamber and the injectors are easy to access.
    One or more may not be spraying properly which would give a misfire that is in turn "hidden" at higher revs.
    A mis-fire can be fuel related as well as ignition related, a poor fuel/air ratio will not ignite correctly. You have eliminated most of the potential electrical faults, your compression is even so time to look at fuel, remember to run you need air (compression), ignition (spark in this case) & fuel. if one of those is not correct you will have issues.

    02 VX, Toyota Alloy Bar, IPF 900XS with 50 watt HID, 50 mm Lift- Lovell Shocks n Springs, Safari Snorkel, large Pioneer tray, Pioneer In-dash, Alpine roof mount DVD screen -handled the Simpson and Innaminka roads, now with a little TRD blower & Unichip


    • #3
      Hello Lee,
      Thanks for your reply.
      At 400ks injectors have always been my thought, but if it was the injectors exactly it would be a constant fualt.
      we in Adelaide just had a horrible heated week, its never been this bad before.
      i notice that it seems to be once the car is dead cold, runs a lot better (almost zero missfire) and then i can park it and come back to 5 cyls again.
      i took it to a mate of mine, he checked everything again. Perfect compression, noid lights worked, said he thinks the injectors are working fine... (i know that they can be clogged and still run) i replaced coils again with a new set i had spare. The leads tested ok too. Plugs are fine and appear to be a good burn.
      He said after everything, try a ignitor module as rhey only last 200k. And maybe a cam angle... for same reasons. I went and tried 3 ignitors and a cam sensor... runs smoother and starts a bit better but no change.
      i managed to finda spare new crank sensor on the off chance and fine too. Mainly as once the engines at temp its an issue.
      i spent all my weekend in the heat trying things, ran the car and pulled injector plugs one at a time and noticed small changes varying.
      i also have run a pinned code check, zero fualts found.
      did a run test, again nothing picked up.
      im starting to think injectors or a pcm fualt.
      its definitely a missfire on a cylinder.
      the clearing i think is harmonics taking over at higher revs, runs very rich at idle ( iac, thermostat and temp sensor replaced and checked)
      ive wiggled and checked all plugs to connectors vigorously too.
      only thing left is injectors or a new car lol.
      its a shame as it is basically new now lol.
      even baffles mechanics.
      i need some one with a diagnosis machine suited for this car i think, but i am just unsure now.
      i appreciate the help, let me know what you think again Lee.


      • #4
        As this engine runs a lost spark ignition, that is the spark plugs fire in pairs, if the issue is spark related you would be dropping 2 cylinders, yes one cylinder is not on compression but having a misfire on 2 out of 6 cylinders should be noticeable. Noid lights really only indicate the electrical signal is present, not any indication of the injector spray pattern/fuel flow etc. I have seen new plugs that are faulty but you had the issue before changing plugs so most likely not the cause.
        I keep coming back to testing the injectors, the plenum gaskets are less than $20 each and it is not that hard to R & R the plenum to access the injectors. There are mobile injector cleaners as well so can be done from home if need be plus having them cleaned & tested will only have good benefits even if not the issue.
        Pops in the exhaust sound like an injector may be dribbling all the time and igniting from exhaust heat. have you checked your fuel rail pressure and leak down?

        02 VX, Toyota Alloy Bar, IPF 900XS with 50 watt HID, 50 mm Lift- Lovell Shocks n Springs, Safari Snorkel, large Pioneer tray, Pioneer In-dash, Alpine roof mount DVD screen -handled the Simpson and Innaminka roads, now with a little TRD blower & Unichip


        • #5

          So TwinkleToeBob I have similar issue, BUT, mine has miss fire when it's cold and when my engine warms up it sounds perfect.
          I bought mine a month ago or so, and when I test drove it first time engine was cold and it was running perfectly. I drove it home and left my Prado in the garage for week or so. Then I took it to pink-slip and notice its a little rough.
          I did get:
          *P0100 Mass or Volume Air Flow Circuit Malfunction
          *P0110 Intake Air Temperature Circuit Malfunction

          After cleaning MAF no codes found, but its still rough as when engine is cold.

          Mine is gas converted and and it has miss fire when cold on both gas and petrol.

          Haven't take it to mechanics yet....hopefully we have someone here who knows how to fix it.