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Troubleshooting 0171 & 0174 Code Help

Discussion in 'Stock 1995 - 2001 Explorers' started by fymbscu, November 16, 2018.

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  1. fymbscu

    fymbscu New Member

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    Just had my fuel pump replaced earlier in the week on Tuesday. Now today, Friday, I get a check engine light and the codes 0171 and 0174. A look under the hood reveals this part with a line freely dangling from it.

    IMG_2202R.jpg

    IMG_2203R.jpg

    I thought the line looked broken, but maybe not, and I don't see an obvious point to connect it to. Could you identify the part for me and where the line should connect to. Been looking through the Haynes manual without success. I am stumped. I expect reconnecting the line will resolve this issue for me. Any guidance greatly appreciated.
     
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  3. ThreeJs

    ThreeJs Active Member

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    That's a heater control valve..
     
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  4. rasouth

    rasouth Elite Explorer

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    ThreeJs called it. That is your heater control valve that connects somewhere underneath all those hoses and black canister to your blower unit. Looks like the hose broke. You might need to splice it together.
     
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  5. 1998Exp

    1998Exp Well-Known Member

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    Indeed, it's the heater control valve. The broken (or more likely, disconnected) line is its vacuum control, which is shared with the vacuum motor that operates the fresh air inlet door. There should be a "T" somewhere near that motor -- which is under the glove box. Vacuum is applied to that motor (and the heater valve) in two positions of the climate control only: "MAX AC" and "OFF". If one of those is selected, there will be a vacuum leak, but I doubt it will be significant enough to trigger the lean codes. The disconnected line should have no effect if any other climate control position is selected. If moving the climate control to any other position does not resolve the lean codes, you have a vacuum leak elsewhere, or perhaps the new pump is not working properly.
     
    Last edited: November 16, 2018
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  6. IronCurtain

    IronCurtain Member

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    I got the same 2 codes a couple days after installing a new fuel pump in my 95 EB last year. Ended up being a faulty pump.
     
  7. rasouth

    rasouth Elite Explorer

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    Could be a dirty Mass Air Flow sensor. Could also be a leak around intake manifold. I had the same problem a few years back and sprayed starting fluid around intake while engine was running and when I sprayed around the leaking area the engine revved up.
     
  8. fymbscu

    fymbscu New Member

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    Thanks all for the identification of the heater control valve. Took another look this morning and see the other end of the break, identified by red circle in photo.

    IMG_2204R.jpg

    It is present in the 2nd photo above also, but hidden under a shadow from the upper piece of the line. Its a tiny line. Not sure how to go about splicing it, rasouth. Is it your opinion that the line is not a replaceable part?

    1998Exp brings up an interesting point about the "MAX AC" climate control setting. Lately, selecting this has sent the airflow to the defrosters until I play with the control to get the expected flow.

    I've cleared the codes for now. Have a short trip this morning. Will see if they return.
     
  9. 1998Exp

    1998Exp Well-Known Member

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    When you select "MAX" (or "OFF"), the vacuum leak through that broken tube effectively disables the control, and it reverts to the default position, which is "DEFROST".

    Hope someone has a magic solution to splice that broken tube. If memory serves, Ford has (or had) a repair kit for those, which includes some sort of special cement. I would try a short section of tight-fitting rubber tube first.
     
  10. rasouth

    rasouth Elite Explorer

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    I've spliced a couple of these small vacuum lines before because they become brittle over time. An ol' timer showed me. He used a piece of tubing that would just fit over old tubing, maybe two-three inches long, and tape both ends. I have used thick wire and stripped the sheathing off and used that. Maybe small water line like from an ice maker or air line from fish tank. A little big but as long as both ends are tape tight it should work.
     
  11. fymbscu

    fymbscu New Member

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    I stopped by an AutoZone and picked up Dorman kit 47430 which contains four miscellaneous size "vacuum connectors," each 2 inches long. The closest fit is a bit loose. Will try to find a better match to the existing line. Any chances of finding the actual replacement part?

    I have an old Power PC Mac and Ford has revised their parts site so that I can no longer get information from them in the TenFourFox browser. Have to use a public library computer now, but Ford also seems to have lost/deprecated info on the '99 Explorer. My VIN draws a blank on their site. Did not find any repair kits listed either.

    The codes haven't yet returned. Will take some more time and get the repair right. Thanks again for all of the input.
     
  12. roscoe 0202

    roscoe 0202 Active Member

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    I had a 99 that would throw that code when it first got cold I reset them and they would stay off for a year
    roscoe
     
  13. fymbscu

    fymbscu New Member

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    Hey guys,
    Sorry for my absence. The power supply on my PowerPC computer went out shortly after my last post. Anyway, I fixed the vacuum line leak with a 5" section of medical-grade vacuum line that fit very snugly over the Ford line, using the friction between the two to keep it in place, although I did add electrical tape to the upper end.

    IMG_2206R.jpg

    Looking at the image above, it looks like a series of three alternately facing clips that might have held the line at one point. I tried using them, but decided against it as I thought it put too much stress on the line.

    I'm not out of the woods yet. Had the 0171 code return on 11/21, and again on 11/26. Then the 0174 code returned on 12/3. Been delayed in replacing my fuel filter because of the computer problems, but wanted to do that before concluding I needed to do something more.

    Your thoughts?
     
  14. Turdle

    Turdle Moderator Staff Member Moderator Elite Explorer

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    Unmetered air ( not measured by the MAF) is getting to the combustion chamber. Vacuum leak somewhere downstream of maf. Check the large intake air tube, brake booster and egr for vacuum leaks. replace intake manifold gaskets.
     

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