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this a miss?

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  • this a miss?

    EEC-IV setup for a thunderbird turbo coupe. I get a miss at or what feels like a miss at steady rpm ranges like during 'normal' driving. As soon as I mash it it goes away. Im thinking that a miss would present it self more during a WOT pull right and might not always go away? This is what leans me to believe it could very well be a fuel pressure problem. A/F ratio bounces around when this happens. Of course this is with a narrow band but as I monitor the gauge even slightly into the gas the gauge will read rich as it is supposed and when the miss comes the gauge will bounce lean to rich. But then again it is hard to tell with a narrow band A/F gauge. the reason Im thinking it goes away when I get onto it is b/c it is a vacuum assisted adjustable fuel pressure regulator, when it reads vacuum the fuel pressure lowers as I climb into boost I am supposed to have 39psi of FP plus what ever boost psi Im running. So 15 psi of boost will bring my fuel pressure to 54. It could be possible the diaphram inside the regulator took a poop and is allowing the intake to pull air/fuel when I have vacuum thru the regulator. What ya think?

    thanks
    Brian

    _________________________________
    65 Mustang 293ci, AOD
    06 Cobalt

    BCP Custom on Facebook

  • #2
    Originally posted by trashline View Post
    So 15 psi of boost will bring my fuel pressure to 54. It could be possible the diaphram inside the regulator took a poop and is allowing the intake to pull air/fuel when I have vacuum thru the regulator. What ya think?

    thanks
    unk: Boost has little to do with fuel pressure and regulators are not vented to outside air to make a lean condition.Vacuum at the regulator pulls against a diaphram,if ruptured it will drawl rawl fuel through the vacuum hose,therefor we would have a rich condition.A non working regulator would make either high or low fuel pressure.Running fuel pressure spec is 30-55 psi.Engine off key on is 35-45 psi.One more thing is that volume of fuel being supplied by the pump is also in question?For that you would need to pull line and perform a koeo fuel volume check.I dont remember the numbers but would expect a pint in 15 sec without to many bubbles.Vacuum hose leaks can also cause a lean trailer hitch feeling.Also remove PCV and inspect ball,these were know for coming appart internally and ball would be missing.Suggest you run EEC KOEO,KOER,before proceeding.Air filter and fuel filters check.I would suspect EGR,remove vacuum line from EGR, plug line,test drive...does it improve or go away?
    A/F ratio is always changing in a computer opperated world.
    Phil
    Friends are like wedgies..They know your inner self..They're intimately close..And it feels great when you pick out a good one.

    Comment


    • #3
      Originally posted by OLE_FORD_TECH View Post
      unk: Boost has little to do with fuel pressure and regulators are not vented to outside air to make a lean condition.Vacuum at the regulator pulls against a diaphram,if ruptured it will drawl rawl fuel through the vacuum hose,therefor we would have a rich condition.A non working regulator would make either high or low fuel pressure.Running fuel pressure spec is 30-55 psi.Engine off key on is 35-45 psi.One more thing is that volume of fuel being supplied by the pump is also in question?For that you would need to pull line and perform a koeo fuel volume check.I dont remember the numbers but would expect a pint in 15 sec without to many bubbles.Vacuum hose leaks can also cause a lean trailer hitch feeling.Also remove PCV and inspect ball,these were know for coming appart internally and ball would be missing.Suggest you run EEC KOEO,KOER,before proceeding.Air filter and fuel filters check.I would suspect EGR,remove vacuum line from EGR, plug line,test drive...does it improve or go away?
      A/F ratio is always changing in a computer opperated world.
      fuel pressure has a direct reference from boost, if it didnt i would lean out so bad even the knock sensor thats unhooked wouldnt be able to pull enough timing. factory fuel pressure is set to 39PSI with a line hooked up. I have mine turned up to 42psi. I run no pcv system either. I realize fuel pressure regulators wont pull air which was kinda why I said air/fuel. I do however get a taste of gas on the vacuum line. I dont think I have a fuel delivery problem as WOT gives me all the fuel I need from the walbro 255lph hp pump.
      Codes i get the one for the missing BCS and once in a while a code 42 which Ive had way before this problem ever came about. This car has no vacuum leaks I pull quite a bit a vacuum at idle and every hose fitting seal tube deal has been replaced and double checked since this happend.

      What I need todo is monitor my fuel pressure and see if this comes up with anything.

      Im way leaned from the ignition now as Ive replaced plugs, wires, cap, rotor, coil twice since this has started over a year ago. Ive also rebuilt the dizzy and Ive switched out my TFI's with three different ones. and no dice.

      hmmmmmmmm....
      Brian

      _________________________________
      65 Mustang 293ci, AOD
      06 Cobalt

      BCP Custom on Facebook

      Comment


      • #4
        Yes,boost needs more fuel to be introduced.Maybe a misread as to what your question was or your out loud thinking,i stand corrected.What i was stating was...Pcm reads Wot which widens the injector pulse by changing voltage which increases fuel to be mixed with the added air,Pump goes into full pressure(vacuum goes to 0 at regulator),timing is adjusted respectivly and everything is just peaches,that i think we already know.My thought is if your pulling an air and fuel mixture through fuel line from the tank this could cause a lean condition,therefor i would check for air bubbles in my fuel system.Monitoring Full pressure dose not always mean that it is just fuel flow and enough volume to satisfy the extra amount of fuel needed.Its been known that a crack in the pick up tube above the fuel level can cause low volume of fuel and a mixture of air.Fuel smell and a code 42 (rich) bad regulator in my thoughts.Code 42 system has been rich for more than 15 seconds when fuel system should have been in closed loop fuel control.If able,monitor your Hego voltage .4 -.7v i think would be good range..1 -.3v would be on lean side .8v and above your on the rich side.Engine temp also important.Air being introduced after the VAF (leak) may be at fault too? Food for thought? Your addaptive controll my not be able to compinsate for the changes you are making.Rule of thumb,PCM built in change of + or -12.5%.By changing and disconnecting and being unable to recalibrate PCM and change perameters that have been factory programed to run in a happy world there way in it self can inflick other problems that may have to be lived with.
        I would be interested as to your future findings.
        Phil
        Friends are like wedgies..They know your inner self..They're intimately close..And it feels great when you pick out a good one.

        Comment


        • #5
          Originally posted by OLE_FORD_TECH View Post
          Yes,boost needs more fuel to be introduced.Maybe a misread as to what your question was or your out loud thinking,i stand corrected.What i was stating was...Pcm reads Wot which widens the injector pulse by changing voltage which increases fuel to be mixed with the added air,Pump goes into full pressure(vacuum goes to 0 at regulator),timing is adjusted respectivly and everything is just peaches,that i think we already know.My thought is if your pulling an air and fuel mixture through fuel line from the tank this could cause a lean condition,therefor i would check for air bubbles in my fuel system.Monitoring Full pressure dose not always mean that it is just fuel flow and enough volume to satisfy the extra amount of fuel needed.Its been known that a crack in the pick up tube above the fuel level can cause low volume of fuel and a mixture of air.Fuel smell and a code 42 (rich) bad regulator in my thoughts.Code 42 system has been rich for more than 15 seconds when fuel system should have been in closed loop fuel control.If able,monitor your Hego voltage .4 -.7v i think would be good range..1 -.3v would be on lean side .8v and above your on the rich side.Engine temp also important.Air being introduced after the VAF (leak) may be at fault too? Food for thought? Your addaptive controll my not be able to compinsate for the changes you are making.Rule of thumb,PCM built in change of + or -12.5%.By changing and disconnecting and being unable to recalibrate PCM and change perameters that have been factory programed to run in a happy world there way in it self can inflick other problems that may have to be lived with.
          I would be interested as to your future findings.
          Code 42 came about once I started modding the car. And installed a bulb in the CEL spot haha. I can grab a used FPR from the junk yard to see if this fixes the problem.
          Brian

          _________________________________
          65 Mustang 293ci, AOD
          06 Cobalt

          BCP Custom on Facebook

          Comment


          • #6
            headed to the junk yard today. Ive been thinking about this for about a week now. I realized that everytime I changed the tfi it had a different effect on the car. The "new" tfi from napa would skitz at cruising speed. the spar eI found started up and gave me a quick problem then went away. Once this started acting up it was bad and it I couldnt really drive it I had ot take an easy.

            So today I grabbed two ford TFIs form the yard for 2 bucks first one I put on and Ive yet to have a problem with it. So maybe this was it. LOL
            Brian

            _________________________________
            65 Mustang 293ci, AOD
            06 Cobalt

            BCP Custom on Facebook

            Comment

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