1994 s-10 issues

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  • 19mopar
    Member
    • Oct 2010
    • 38

    1994 s-10 issues

    VIN 1GCCT14W4R8166478 OBD 1 Vehicle has intermittant rough idle and stall. Performed fuel pressure tests, ok. Did notice that fuel pressure regulator under upper intake is clean on side towards front of engine but fule pressure holds and see no fuel dripping out when pump is commanded on. Found no fault codes but LT fuel trims are 115 or lower. What is odd is that when thottle is closed the fuel trim cell is at 4 and I think it should be 0 which is idle and no load. Also if throttle is applied just slightly while in park the trim cell jumps up to 16 which I understand to be max rpm and max load. The MAP TPS and Oxygen sensor check out ok. Possible bad ECM? But if vehcle is driven the fuel cell trim will be between 4 and 10 under different throttle positions.
  • Orevin
    Senior Member
    • Aug 2010
    • 1110

    #2
    How about a stuck open EGR valve? I have also seen carbon build-up in the throttle body causing similar symptoms on this engine.
    -Kai-
    Chicago, IL

    Comment

    • 19mopar
      Member
      • Oct 2010
      • 38

      #3
      The EGR data is correct and when commanded open the pid data shows EGR Position exactly where it is commanded to. I have tried a used ECM and that didn't change the problem. I will most likely pull the EGR and inspect visually and then pull upper intake and visually look at all the injector tubes to rule out a split or crack in one of the tubes where i can't get the bore scope probe. Another question, what closes the poppet valve on the end of the injector tube. The verdict won't do and injector balance test like on the OBD II vehicle with the same injector setup so i don't know if maybe a poppet valve is sticking. Thanks.
      Last edited by 19mopar; 04-27-2011, 01:33 PM.

      Comment

      • SnapOnKid
        Senior Member
        • Jan 2011
        • 870

        #4
        Originally posted by 19mopar
        The EGR data is correct and when commanded open the pid data shows EGR Position exactly where it is commanded to. I have tried a used ECM and that didn't change the problem. I will most likely pull the EGR and inspect visually and then pull upper intake and visually look at all the injector tubes to rule out a split or crack in one of the tubes where i can't get the bore scope probe. Another question, what closes the poppet valve on the end of the injector tube. The verdict won't do and injector balance test like on the OBD II vehicle with the same injector setup so i don't know if maybe a poppet valve is sticking. Thanks.
        could be a poppet valve issue as you pointed out. They are pretty common but with out a way to test it, it will be hard to pin point. Try puting some fuel treatment in it and see if it changes...

        Comment

        • Joe Rappa
          Snap-on DSD
          • Aug 2007
          • 2050

          #5
          Originally posted by 19mopar
          VIN 1GCCT14W4R8166478 OBD 1 Vehicle has intermittant rough idle and stall. Performed fuel pressure tests, ok. Did notice that fuel pressure regulator under upper intake is clean on side towards front of engine but fule pressure holds and see no fuel dripping out when pump is commanded on. Found no fault codes but LT fuel trims are 115 or lower. What is odd is that when thottle is closed the fuel trim cell is at 4 and I think it should be 0 which is idle and no load. Also if throttle is applied just slightly while in park the trim cell jumps up to 16 which I understand to be max rpm and max load. The MAP TPS and Oxygen sensor check out ok. Possible bad ECM? But if vehcle is driven the fuel cell trim will be between 4 and 10 under different throttle positions.
          A fuel trim in the neighborhood of 115 is not the greatest, but it wouldn't scare me too badly on this truck, and I doubt it is the cause of it running poorly.
          The fuel cell jumping around like that is normal.
          If the intake is clean around the regulator, you know that sucker is leaking, but if it's not losing fuel pressure, and the fuel trims aren't way out of whack (and they're not) it's probably not the cause either.
          I would suspect an injection spider before I suspected the ECM on that truck, but I think you're going to have to gather some info when it's performing poorly. See if you can't catch the data with a snapshot. It would help a lot to see all the data when it's goofing up.

          Joe
          "You don't build a reputation on what you're going to do"
          Henry Ford

          Comment

          • 19mopar
            Member
            • Oct 2010
            • 38

            #6
            Ok here is an update on this vehicle. Removed upper intake and found slight crack in fuel injector tube and front side of fuel injector looked to be washed clean with fuel. Replaced injector assembly with tubes and poppet valves. Removed EGR valve and inspected and cleaned. Cleaned throttle body plate and bore. Remove IAC and cleaned. Started vehicle and vehicle started better but still would idle rough and stall if put into gear. checked battery terminals and cleaned. Tried used ECM, no change. Removed all vacuum lines and plugged ports on intake, no change. Blocked off PCV valve and installed propane through oil dipstick tube at idle, no change. Now when monitoring EGR pos compared to EGR commanded it would go as high as 99% when EGR is not commanded and stall this was worse in reverse than drive and sometimes would idle fine in drive but stall in reverse. when it would start to run bad the egr position would be shown as open/un-seated but it was allways commanded at 0% Checked wiring for egr, ok. Replaced EGR and did same thing. First pic is idleing in park and second is idleing in reverse. Was wondering what could be useating/opening eger fully when in reverse. When idleing in drive the EGR is zero. Thanks will try to figure out how to post some more info later. i have pid data captured in a video but couldn't get it to upload at this time, kinda new to posting this kind of stuff but love my Verdict. Also the oxygen sensor will stay on the rich side when the EGR pos% is greater than 0 whick is telling me that in fact the EGR is open. The o2 pid will cycle normally when the EGR is the same as the Des EGR. Thanks
            Last edited by 19mopar; 07-30-2011, 04:09 PM.

            Comment

            • 19mopar
              Member
              • Oct 2010
              • 38

              #7
              Ok here is a snap shot in graph form of the Des EGR compared to the EGR pos idleing in reverse
              Last edited by 19mopar; 07-30-2011, 04:09 PM.

              Comment

              • jonage
                Member
                • Oct 2010
                • 35

                #8
                did you ohm out the cap?
                theres no car that i can't break.......

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