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Thread: OBD II Code 171

  1. #1

    Default OBD II Code 171

    I have a '96 Contour with a 2.0. Check engine light came on with code 171. Changed the O2 sensors and cleaned the MAF (about 1 year old).

    I looked all over the engine and don't see any visual issues. I changed the fuel filter. Draining it produced some metal flakes, plastic pieces (not much of either) and a bit of water.

    I hooked up a vacuum gauge and at idle it reads between 13 and 17 inHg. Very low in my opinion, but I don't know what it should read. The vacuum was steady , only pulsing as idle speed changed. I looked around some more, but I don't see any obvious signs of a leak. I sprayed carb cleaner at all the likely spots, but no change in idle.

    I would like to test the fuel pressure, but my software won't test, only read. i think I can get a gauge from the local parts store for testing. Is there a way of getting full fuel pressure without a test program?

    Steve

  2. #2
    Join Date
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    There should be a Schrader valve on the fuel rail that you can plug the test gauge into to check fuel pressure

  3. #3
    Join Date
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    that vacuum reading sounds good to me. I forget what my zetec was reading, I might have posted it somewhere previously. You can check the fuel pressure from the fuel rail.
    - 12 Focus SE
    - 95 Mystique LS <-sold
    - 99 Contour SE Sport <- traded in 2/13
    - 99 Contour SeVT <- 3L/NPG Turbo
    - 2k Contour SVT - #2137

  4. #4

    Default

    Glad to know the vacuum is OK. I am used to SBC's with 20 to 25 in Hg at idle.


    I would love to test the fuel pressure at the fuel rail, but I don't have a way to tell the computer to run the pump at full output. My shop manual says to plug in a guage and then run a pump test via a scan computer. I have scantool, but the free read only version. Is there any other way to test properly?

    Yesterday I tried to pull the car into my garage and it took nearly 5 minutes to get it started. After it started it ran rough for a good 15 seconds.

    Steve

  5. #5
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    the Ford manual will call out a idle fuel spec, I would start with testing and see where the pressure is. Then I believe the manual will also give an off idle value which can be checked for by reving the engine.
    - 12 Focus SE
    - 95 Mystique LS <-sold
    - 99 Contour SE Sport <- traded in 2/13
    - 99 Contour SeVT <- 3L/NPG Turbo
    - 2k Contour SVT - #2137

  6. #6

    Default

    I guess it depends on the manual. The Haynes guide I have says to test with the engine off. I can test with engine on if someone knows the proper values?

  7. #7

    Default Resolved

    I replaced the fuel pump and that appears to ahve fixed the issue. The engine runs better, no more hard starting issues, and no codes.

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