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EGR Modulator

Discussion in '80-Series Tech' started by landtoy80, Jan 9, 2004.

  1. landtoy80

    landtoy80

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    Seeing Darwood's modulator http://homepage.mac.com/darwood/egrmodulator3.jpg
    (I don't know how to steal his pic :-\ Someone please insert his pic of the carboned modulator ) has me thinking that a bad modulator could be the reason the rest of the EGR system fails.
    The bottom port on the mod. is hooked up via a vacuum hose, to the EGR pipe from the exhaust. Hot exhaust gas is what pushes the diaphragm of the mod in. When the mod's diaphragm gets a leak in it, carbon can get into the vacuum system of the EGR system (not good :'( )

    With carbon in the vacuum system, the VSV can/could get plugged or damage the diaphragm of the VSV. Or (like on mine) the VSV would work one time I test it. Then the next time I test it it fails. Carbon could be getting stuck in the port of the VSV, triggering a code. Then the carbon gets sucked though the VSV and all is fine but there is still a code in the computer. When you go to test the VSV it tests fine.

    I could be way off on this but think that carbon should not be in the vacuum part of the EGR system.
     
  2. T Y L E R

    T Y L E R

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  3. Junk

    Junk

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    So you're thinking, maybe every 50-60k or more, maybe just swap in a new modulator? Could make sense.
     
  4. landtoy80

    landtoy80

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    Has anyone had porblems with the new/fj60 modulator?
    Could be the 80 mod was a bad part.
     
  5. Beowulf

    Beowulf

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    Kurt,

    That sounds like a reasonable theory to me. My VSV failed and replacement over a year ago has kept me P0401 free. The resistance across the terminals was extremely high. If your theory is correct, the cause could be from carbon entering the VSV and "shorting" the terminals. Carbon conducts electricity, right?

    When you opened your VSV did you see carbon deposits internally? Did you take any pics of the VSV internals?

    -B-
     
  6. semlin

    semlin discouraged user

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    if there is not supposed to be carbon in the vacuum lines then why is there a filter in the vacuum portion of the modulator to catch carbon??

    I do agree with the idea that too much carbon is probably a bad thing for the vsv. I can't think of another reason why this part would keep failing unless it is heat related. The cheaper solution to me is to clean your modulator filter often and even to replace the filter regularly (if someone can figure out how to purchase the filter alone).
     
  7. Beowulf

    Beowulf

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    Simon,

    When my truck started giving the P0401 at about 97k miles, the EGR modulator filter was white, almost no carbon deposit at all. It looked almost new.

    -B-
     
  8. semlin

    semlin discouraged user

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    hmm. at 135k mine had so much carbon that the filter bottom had a smooth black layer about 1 mm thick, and there was not a trace of white anywhere in the filter. This is why I am replacing everything, including vacuum hoses.

    Just picked up my 3 foot extension bar on the weekend.
     
  9. Scamper

    Scamper

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    I'm in favor of just changing out the filter every now and then. Heck, they made it so dang easy to do, you could do it every oil change (so long as Mr. Toy doesn't charge $10 for what amounts to a small Stridex pad).

    Anyone know if you can buy these all by themselves?

    Tom
     
  10. Junk

    Junk

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    I doubt you can, but maybe Cdan could let us know.

    If not, maybe just finding something similiar after market to cut and put in there makes some sense.
     
  11. Gundy

    Gundy

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    I'm checking that sucker with the next oil change. Just curious.
    Our's was off white gray with a pencil eraser sized black dot on the
    bottom of the filter. I flicked the black dot off and then ficked some
    more light dust out of it. Put it back in. 116k miles. MIL is still out
    100 or so miles later with highway and some city traffic. Several trips.
    It did idle like sh*t till it righted itself. 250rpms at idle. For a couple
    or few start/stops. I had disconnected the battery.
    The MIL had only just appeared. Like within 50 miles of the carbon flick off.
    I'm curious what will be there at the next check. The bottom part of my modulator
    looked like new.
    In the meantime, I'm knocking on wood and chantiing.
    Boy I'd like a source for "new" filters comparable with the oem one too.
    :rolleyes:
     
  12. JJcruiser

    JJcruiser

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    I've had the dreaded "401" engine light come on and checked my modulator brillo pad. It wasn't nearly as black as his, but it was brown enough to warrant replacing. You can't buy just the filter, you have to purchase the entire modulator which runs over $40. I wen tto Kragen, found a filter with similar pattern and density, bought it for $1.50 and cut it to fit. Seems to work just fine!
     
  13. Darwood

    Darwood

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    Well I replaced that ugly modulator and got one with a part number ending in a 1 instead of a 0. I assume this is the fj60 modulator. I can't figure out how to get to the filter. Since it was a new part I didn't pry to hard at the cap, but it seems to me that you can't get it off in comparison to the old part.

    I'm also fearful that the VSV might be ruined since my modulator looked soo good. Also notice the little puddle of water that was there from the engine detailing. I need to post pictures of my motor. It's hella clean.

    I agree that much carbon floating around in vacuum lines can't be good.


    I haven't driven much since the modulator replacement (mainly due to the fact that my truck isn't registered) but the light has stayed off so far, and there are no stored codes in the ECU as of the last time I checked.
     
  14. semlin

    semlin discouraged user

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    Darwood why would you put a different modulator in there? I am confused.

    for those making their own filters keep in mind the factory filter is made of two materials. One side is rougher than the other.
     
  15. Riley

    Riley

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    Seems to me that there is a root cause or reason that the filter is getting soooo dirty. This can't be normal. I wonder if it's cause the PCV is clogged or some other reason.

    Does anybody know why they get so dirty on some trucks and not on others (with similar mileage)?
     
  16. semlin

    semlin discouraged user

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    Riley, i am guessing the modulator valve eventually goes bad sticks open and admits way more carbon. Might this also explain the heat damage I had to my vacuum hoses?
     
  17. Darwood

    Darwood

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    semlin,

    Well I placed a different modulator in there since that's what the Toyota parts guy gave me for my truck. When I got it home I noticed the part numbers differed by 1 number and that they looked relatively the same. They just had some small differences. I just figured it was an updated part. The new part has a blue label on the top that say denso, where as the old part had a green label on the top that said denso. Both of them have the Q, R, and P (if memory serves correctly) hose connectors as well as the hose connector to the exhaust on the bottom. The new part fit fine.

    I'll go post part numbers when I get home.
     
  18. Darwood

    Darwood

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    Ok I have the part numbers now, the old EGR modulator was:

    25870-66010

    and the new part is:

    25870-66011
     
  19. landtoy80

    landtoy80

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    from left to right
    fj60, new fzj80, old fzj80
    The new 80 modulator is a Toyota replacement for the fzj80.
    Is is the same as a fj60 modulator.
     
  20. landtoy80

    landtoy80

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    The filter has nothing to do with keeping carbon out of the vacuum system.
    The fiter is on the top of the modulator.

    The hot carbon filled exhaust enters the modulator from the bottom of the modulator. There is a diaphragm that the exhaust gas pushes. When the diaghragm gets a leak. Carbon and hot exhaust gas gets into the modulator.
    This can explane why some have rotted vacuum hoses.

    B- I only had a little bit like 5 to 10 chuncks of carbon in my modulator when the VSV failed. There was no carbon in the VSV when I took it apart but I might of blew thew carbon out when I was testing with vacuum gage and my mouth.
     
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