1997 F250 5.8 open or closed loop

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  • quickhitch11
    Member
    • Aug 2012
    • 78

    1997 F250 5.8 open or closed loop

    Hi all,
    Have a friend's F250 that has 128,00 on the odometer, but new motor last summer. It has an issue at idle. It will stay in open loop, even at 190+ temp. I am planing on scanning it this week, did it last fall, for a diff issue. I was looking around and find conflicting info on this. I remember it was staying open, until you just brought it up from idle, then it goes into closed loop. While at idle it is extremely rich, you cannot stand around it for long, it gasses you out. Was wondering if it is norm for this, could be idle too low, as i said i will put the verus on it this week and watch what happens. The O2 sensor is new Ford sensor done at motor swap, only has the one downstream of the Y pipe connection. Looking for some direction
    Thanks in advance, Chris
  • Crusty
    Senior Member
    • Dec 2007
    • 2450

    #2
    The open-loop at idle does ring a bell. Take a look at idle LTFT and see what it says and then watch the STFT and the LTFT once you're off idle.
    I have seen a couple (not many) but apparently these are common for mis-reporting MAF volumes which would affect fuel learned values.
    Also vacuum leaks from various rubber hoses and tubes are common, possibly at the base of the throttle body feeding the PCV system-??

    Comment

    • quickhitch11
      Member
      • Aug 2012
      • 78

      #3
      Thanks Crusty. I will be looking at it possibly tomorrow evening. Will let you know what I see. Motor change was done last summer, but think it was always an issue even before that was done. This was a Ford short block job, he did himself. Will get back to you. Thanks again, Chris

      Comment

      • quickhitch11
        Member
        • Aug 2012
        • 78

        #4
        One other q. Any thought on the idle rpm?

        Comment

        • badcoupe
          Senior Member
          • Jan 2011
          • 218

          #5
          check fuel pressure I've had a few with the regulator stuck and had 70+ pounds of fuel pressure

          Comment

          • Witsend
            Banned
            • Nov 2012
            • 2942

            #6
            Leaking fuel pressure regulator

            Fuel trims at idle very negative indicating very rich . Check fuel pressure for excessive leakdown , Check for leaking fuel pressure regulator leaking raw fuel into vacuum hose, collapsed PCV hose not leaking vacuum yet (a vacuum leak however will cause excessively lean condition , but if just collapsed upon itself could make things richer, since there be more vacuum to pull more metered air through the MAF sensor since the unmetered air going through PCV valve be cut off or restricted by a collapsed hose .

            Comment

            • Crusty
              Senior Member
              • Dec 2007
              • 2450

              #7
              Originally posted by quickhitch11
              One other q. Any thought on the idle rpm?
              One step at a time. Check the fuel trims. It sounds as if it's getting too much fuel, or not burning all that it is getting.
              In open loop, the STFT should be at 0, and not updating/learning, but the LTFT will tell you what it is getting.
              If the idle speed is blipping up and down, check the TPS and the TAB. Fuel pressure testing is certainly a good starting point as soon as you have gathered your scan data and done the visual check.

              Just to illustrate the importance of logical basic checks and tests; a Ford truck had been to 2 shops and the dealer (three shops) and it ran like a real dog with all sorts of problems/issues. The air cleaner boxes of this era would spin the cover bolts because the plastic didn't hold the nuts in the lower housing. No one could get the air filter out. Well over 1500 dollars later and three shops later, I fought with the air cleaner and found a solid plugged brick instead of what had been the air filter. As it happened, ALL the driveability and starting problems were solved with a new air filter.
              SOME of the things the other shops did were probably necessary but possibly not all. The guy was mad as a hatter at ME.
              Basics first. No assumptions.

              Comment

              • lancepoulin@msn.com
                Junior Member
                • Sep 2011
                • 17

                #8
                air filter brick points me towards escewed maf. fuel pressure check first. test maf at idle and above. graph urstream 02 sensors and do snap throttles and watcj what they do at snap. they will still report aslong as therr hot enough even in open loop. revisiting i stallation of longblock would b instrimental as well. good luck

                Comment

                • quickhitch11
                  Member
                  • Aug 2012
                  • 78

                  #9
                  Just an update, i was able to scan the truck on Monday, but had to run out of state for family. I am trying to upload the files to a mem stick to transfer to the laptop, but have been having an issue with my computer.
                  I did notice a couple of things, this is only accessable from under the hood, and i only see short fuel trim, no long. Also we noticed it was not able to make coolant temp above 176'. I ohm'd out the temp sensor, and it is accurate according to info we had from manual. Also checked it with a IR reader and temp is correct. Same thing with the loop, is always open at idle, but will close as soon as you bring it up. The idle is also running @ over 800 rpm which seems too hi, but not sure if it can be changed, or is being held because of temp. He changed the the thermostat while i have been gone, and it is now up to 190 to 195. Also it only has 1 02 sensor.
                  If memory is correct, at idle the 02 was very low, but does begin switching when you bring rpm up.
                  I will be posting the recordings as soon as i can
                  thanks again, chris

                  Comment

                  • quickhitch11
                    Member
                    • Aug 2012
                    • 78

                    #10
                    OK, i think i have this right. Here are 2 diff files from the F350. I was looking at these in ssc. This is so much easier to read on the laptop. I was wondering why there is no long term fuel trim. I figure it is the OBD1 ?? Also the throttle position switch voltage seems off in the 17.49 pids?? Trying to learn, but feel a bit lost. You had mentioned that the short fuel trim should be at 0 in open loop, but this is not. Any help would be greatly appreciated, Chris
                    Attached Files

                    Comment

                    • Witsend
                      Banned
                      • Nov 2012
                      • 2942

                      #11
                      All USA cars and trucks sold in 1996 were supposed to be OBD 2

                      Put the Verus down and Try a generic ODDII EOBD II generic scantool like a Harbor Freight Autel Knock Off and I'm sure it will display a pid for LTFT,

                      Comment

                      • Crusty
                        Senior Member
                        • Dec 2007
                        • 2450

                        #12
                        Originally posted by quickhitch11
                        OK, i think i have this right. Here are 2 diff files from the F350. I was looking at these in ssc. This is so much easier to read on the laptop. I was wondering why there is no long term fuel trim. I figure it is the OBD1 ?? Also the throttle position switch voltage seems off in the 17.49 pids?? Trying to learn, but feel a bit lost. You had mentioned that the short fuel trim should be at 0 in open loop, but this is not. Any help would be greatly appreciated, Chris
                        There are several Fords, particularly the 3/4 ton and 1-ton that were allowed special permission to not be fully OBDII compliant between 1996 and 1999. It wouldn't surprise me if this was an OBD-I vehicle, usually depending on the GVWR.
                        See what data you get in OBD Direct. If all it is doing is going "open loop" at idle, I wouldn't worry about it. What else is the vehicle doing that is giving you problems-??
                        Did you connect under the hood or under the dash-??

                        Comment

                        • quickhitch11
                          Member
                          • Aug 2012
                          • 78

                          #13
                          The main reason I looked at it for him was the rich contition at idle. If it is left idling it chews through fuel. I hooked up under the hood, 2 plugs and connect to the battery. I never thought About going obd direct. I just assumed ( bad thing to do, I know) that what I was looking at on the scanner was all that was available.I will check it again and see what I get. I get conflicting answers too the question about it going into open loop at idle. Is it supposed to, or not, and it is idling at 800+ rpm which seems to high. Any thoughts, thanks again, Chris

                          Comment

                          • Crusty
                            Senior Member
                            • Dec 2007
                            • 2450

                            #14
                            Originally posted by quickhitch11
                            The main reason I looked at it for him was the rich contition at idle. If it is left idling it chews through fuel. I hooked up under the hood, 2 plugs and connect to the battery. I never thought About going obd direct. I just assumed ( bad thing to do, I know) that what I was looking at on the scanner was all that was available.I will check it again and see what I get. I get conflicting answers too the question about it going into open loop at idle. Is it supposed to, or not, and it is idling at 800+ rpm which seems to high. Any thoughts, thanks again, Chris
                            I forget exactly where I sourced this online but here is what Ford published for the 1997 M/Y.
                            Read away.....

                            Years ago, a SnapOn "trainer" said to me "you save too many files"....
                            Attached Files

                            Comment

                            • Crusty
                              Senior Member
                              • Dec 2007
                              • 2450

                              #15
                              Originally posted by quickhitch11
                              The main reason I looked at it for him was the rich contition at idle. If it is left idling it chews through fuel. I hooked up under the hood, 2 plugs and connect to the battery. I never thought About going obd direct. I just assumed ( bad thing to do, I know) that what I was looking at on the scanner was all that was available.I will check it again and see what I get. I get conflicting answers too the question about it going into open loop at idle. Is it supposed to, or not, and it is idling at 800+ rpm which seems to high. Any thoughts, thanks again, Chris
                              Check the BASE idle speed....has someone turned the screw-?? What does the TAB do, in park/neutral and also in gear. Does it recognize the PRNDL input-?? What is the base timing setting-?? There is also an "octane adjustment" jumper on a lot of Fords of that era. Does the idle come down about 150 to 200 rpm when you go from park to drive-?? Does it change when the A/C compressor is commanded on....and don't forget that any "defrost" mode IS an A/C commanded position....
                              As for chewing thru fuel....well.....up here in the great white north there were not ANY Fords back then that actually got even close to the "advertised claims" for fuel economy--ROFLMAO.

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