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Exhaust, Overheat and O2 Sensors

Discussion in 'Honda Acty' started by Littlestan, Sep 20, 2014.

  1. Littlestan

    Littlestan Member

    Hey all,

    Was driving along the other day and the exhaust overheat indicator on the dash lit up (the red one that looks like a muffler with wavy lines over it). Got
    to where I was going, parked it for my 8 hour work shift, then started it up again from bone cold... and the light came on again immediately.

    Thought this was strange as the truck was running fine and all fluids are good/engine temp gauge showed normal, so I hopped out and
    looked underneath; sure enough the overheat sensor wire had rusted clean off the sensor and is currently dangling from the wire harness.

    Would anyone have any idea for a replacement part number for the overheat and 02 sensors on the exhaust? This is actually pretty good
    timing as I'm going to be getting a whole new exhaust for the truck in a month or so anyways since the current one is rusting apart quickly.
    Actually, would anyone have an idea where to get a full exhaust setup for that matter? I figured I'd just have to get some quotes for one to
    get made up, but if there's anywhere that would know differently, it would be here. :)

    Thanks,
    -Stan
     
  2. OldMachinist

    OldMachinist Moderator Staff Member

  3. shogun

    shogun Active Member

    37810-PZ3-903 THERMO SENSOR, CONVERTER (NGK)
    Here you can see the location of that part on the exhaust, check the 2 wires and the plug
    http://jp-carparts.com/honda/partlist.php?maker=honda&type=ACTY TRUCK&cartype=30822&fig=E&fig1=400

    Exhaust part numbers are here
    http://jp-carparts.com/honda/partlist.php?maker=honda&type=ACTY TRUCK&cartype=28985&fig=B&fig1=200
    based on what I selected:

    car name ACTY TRUCK
    model name M-HA3 (11SJ701)
    classification number 6476-012
    chassis no 1000001 - 1047932
    note SDX
    AT/MT AT
    Engine E07A

    double check part numbers based on your chassis number
     
  4. Littlestan

    Littlestan Member

    Thanks OldMachinist for the link to yokohama; I always forget to check there! And thanks
    to shogun for the additional information, that will definitely come in handy in the future. :)

    Just gotta track down an O2 sensor and I'll probably have to get an exhaust made up locally.
     
  5. Littlestan

    Littlestan Member

  6. OldMachinist

    OldMachinist Moderator Staff Member

    The muffler in your Ebay link is what's on my truck. The hose connections pull air out of the right side frame rail and over the muffler to supply warm air to the air filter box.
     
  7. Littlestan

    Littlestan Member

    Morning! Thanks for the super quick reply OM! :)

    Good to know about the warm air system... I should probably just snag the one off eBay to keep it all functioning as normal then.

    As a side thought; should I be unhooking or plugging these hoses in the summertime when the engine would much prefer a
    colder, denser air charge?
     
  8. OldMachinist

    OldMachinist Moderator Staff Member

    There's temp controlled door in the air filter box that closes off the preheated air in warm weather.
     
  9. Littlestan

    Littlestan Member

    Back again with a progress report!

    After talking to my local exhaust shop and learning that even if I ordered the replacement exhaust that I would have to replace
    or delete the catalytic converter (as mine was FUBAR), I decided to go with a total custom replacement. Result is amazing!
    Extremely quiet now, highway road noise is wonderful; my radio now only needs to be turned up to 20 instead of 30 to hear clearly.

    I had the exhaust guy retain the air warming system and weld on bungs for my future exhaust overheat sensor and a narrowband
    sensor I had kicking around. Here's where some strangeness comes in... as he was showing me the finished exhaust up on the hoist,
    I asked him where the O2 sensor was. He looked at me a bit funny and said he didn't see one so didn't add a bung for it. We looked
    at the old exhaust together and sure enough, there was only the one bung for the overheat sensor. Went back to the truck and looked
    at the exhaust manifold itself to see if it was mounted on there instead. Nothing.

    Isn't there supposed to be an O2 sensor? I see one on the diagrams as shown at:

    http://jp-carparts.com/honda/partlist.php?maker=honda&type=ACTY TRUCK&cartype=30949&fig=E&fig1=400

    Just crawled under the truck again tonight and confirmed that there was no dangling electrical connector which would
    suggest a missing O2 sensor. It's MUCH easier to see how everything is tied in down there now with the new exhaust
    since there's no crazy heat shields on everything, so am I just missing something?

    1994 E07A, 5 speed manual w/AC.
     
  10. OldMachinist

    OldMachinist Moderator Staff Member

    The diagram you linked to shows that there were 2 different styles of convertors, one with the sensor(#15) and one without(#5). Even the shielding is different between the two.
     
  11. Littlestan

    Littlestan Member

    Hey again OM! Thanks for your expertise on the matter once more...

    I did notice the two different types of catalytic converter and confirmed at the shop that there was no O2 present on it.

    However, the overheat thermo sensor (#9) is what's throwing me for a loop. It appears to be attached directly to the exhaust manifold or
    close to it, where the bung for it is originally from wayyy in the back of the exhaust system, close to the muffler itself.

    So as far as you can tell, is this normal? I find it bizarre that it wouldn't have a O2 sensor to begin with coming from Japan and their
    uber smog restrictions, but if all's well then at least it saves me from having to replace another part! :D
     
  12. TRAX and HORNS

    TRAX and HORNS Well-Known Member

    If you have a new exhaust system forget the sensor unless you just want it. The wire that rusted into, ground it out to the frame and it should kill the light in dash.
     
  13. Littlestan

    Littlestan Member

    Oh yeah, I'm actually happy that there isn't one since it means one less part to replace/go wrong. :) I'll either bypass the overheat sensor
    circuit like you suggest or remove the bulb from the panel. I can't see me dropping $150 for a new one anytime soon.

    Instead, I'll invest in a rebuilt carb from Yokohama. I had to do the solenoid bypass trick that OM posted a few years back and it's definitely
    the stock carb on there still. Got a bit of rough idling and etc. Figure I should replace it before something major happens.

    Thanks for all the help guys!
     
  14. OldMachinist

    OldMachinist Moderator Staff Member

    Attached Files:

  15. Littlestan

    Littlestan Member

    Awesome, thanks for the clarification OM! Exactly the same position as mine was. New (rebuilt carb) it is! :D

    If it can stop raining for a few hours here I'll post up some pics of the new exhaust for y'all.
     
  16. Littlestan

    Littlestan Member

    20141024_111940.jpg 20141024_112037.jpg 20141024_112048.jpg

    You can see where the original overheat sensor bung has been moved closer towards the engine, with the new
    narrowband sensor welded about 8 inches behind it. I'll be removing it soon to sandblast and high temp paint it
    for long term protection, should outlast the life of the vehicle then. I really like the easy 3 bolt clamping at all the
    section joints. Much easier to work with than rusty studs.
     
  17. Aloha,

    I was driving home tonight and my overheat sensor light came on as well as my battery light. Only a short drive for me so I put it in the driveway and shut down. Both lights lit up again immediately upon restart.

    I plan to get into this on Tuesday but just curious if anyone else has seen both the battery light AND the overheat sensor light on together. I plan to start by looking for a bad ground. Battery is new.

    The odd thing is that I always have high idle until the temp comes up after rebuilding the top end. (broken timing belt : minitrucktalk.com/threads/how-to-change-timing-belt-and-water-pump-on-an-acty-video.18741/) and this evening when I started it after 12 hours in the parking lot I noticed it was idling lower than it's normal cold start.

    It is a '92 Acty "Attack"

    I will start at the exhaust overheat sensor and work out from there but I am curious as to why the battery light was on as well

    Thanks to everyone for the helpful info on this site
     
  18. shogun

    shogun Active Member

    too low voltage can cause control modules and relays play crazy. and show faults, even can cause malfunctions of the ECU and trans control. First of all check the alternator output, because when the engine is running the alternator should have enough power to supply the modules and recharge the battery.
    Maybe voltage regulator problem or defective diodes in the alternator, alternator belt slipping.
    Of course also bad grounds can cause problems.
     
    Last edited: Apr 6, 2022
    fmartin_gila likes this.
  19. Thanks shogun,

    I finally had a chance to look at it in the daylight and my alternator belt was completely shot. Glad it is an easy one!
     

    Attached Files:

    shogun likes this.

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