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Ghostly cylinder 3 misfire

Discussion in 'Other Vehicle Discussions' started by UNDR8D, Jan 13, 2010.

  1. UNDR8D

    UNDR8D ...has a job!

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    OK, I know this is not Honda related but I'm a regular so leave me alone...

    My wife's 96 Toyota Avalon 3.0 (1MZFE) has had an intermittent, inconsistent, and utterly confounding cylinder 3 misfire for the past three weeks.

    It comes and goes with no apparent pattern or ties to any other condition. The misfire is ONLY on cylinder 3 which is in the middle against the firewall.

    This motor has DI so it has individual coils over the front three plugs with traditional wires traveling from those coils to the back three cylinders. The #6 coil feeds the #3 cylinder.

    Here's what I have done:

    -replaced plugs for a baseline b/c it needed them anyway

    -replaced plug wires from the front 3 to the back 3, also b/c it needed them.

    -tested the resistance of all coils...all within spec.

    -spark tested from coil to wire and from wire to plug while it was running poorly and running well...it had strong consistent spark at all times...


    Here is why the misfire is so mysterious. It comes and goes for no apparent reason. Sometimes it misfires on start up. Other times it runs fine then starts misfiring. It does it when the outside temp is freezing (5 F), cold (20 F), or warm (30s). It does it at any time regardless of engine temp.

    Sometimes it runs great for a few days then starts to do it again for no reason.

    We know that it is not ignition related b/c it always has good spark.

    Sometimes it will start misfiring while driving then stop a mile or two later...WTF?

    I have ruled out the ECU b/c it is isolated ONLY to cylinder 3 and generally, a bad ECU will produce a random/multiple misfire code.

    I have ruled out a mechanical problem b/c:

    a) it is a Toyota
    b) it is very intermittent
    c) it sounds fine and runs well otherwise

    I doubt the ignition coil would be so on and off...generally they just fail and there is no going back to good.


    I think it may be a sticking injector. It does seem sometimes as if getting near or going below 1/4 tank of gas causes the problem but this has yet to be consistent and again, why would it be only on the #3 cylinder.

    So, I'm going with sticking injector for now. I have to pull the plenum off so I can get to the injector to test it. I dumped a bunch of Lucas injector cleaner in the car and it seemed fine for a couple days but now it is doing it again. I am getting sick of driving Katie to work...I need some ideas:confused:
     
  2. UNDR8D

    UNDR8D ...has a job!

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    *bump* cmon srsly? no ideas?
     
  3. eg6sir

    eg6sir Supa Mod Moderator VIP

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    :moved: to the correct forum
     
  4. klyph

    klyph Dismember VIP

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    Have you checked the connection to the injector?

    My bet is still a bad coil.
     
  5. UNDR8D

    UNDR8D ...has a job!

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    Thanks eg6

    And Klyph, I'm going to clear the codes and move the coil. If the misfire follows the coil, then I'll replace it.
     
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