still can't get rid of misfire!

Discussion in 'SN95 4.6L Mustang Tech' started by stangGT97, Mar 30, 2006.


  1. dz7b7h

    dz7b7h New Member

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    It may sound a little daunting for someone with no car experience but it really isn't that bad. Take it from someone who knew nothing about cars before I bought my Mustang. I've learned a lot since then. It did help that I had an extra vehicle at the time. It can get very frustrating and discouraging but don't give up. I think our year model car is very finicky about what is done to it. I am sure to do very thorough research now to see how my mods will effect the car. Planning is the key. Always give yourself plenty of time so that you don't have to rush and possibly miss a step. If you have any questions about what I wrote feel free to PM me. Hope this works for you. Later. D. :flag:
    #81
  2. stangGT97

    stangGT97 New Member

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    wow, there was a lot of effort involved in that post and I really appreciate it :hail2: . Couple of questions for you:
    1. When do you plug your IAC back in? Or do you not do that?

    actually that was only 1 question but oh well. Thanks a lot for the help!
    #82
  3. dz7b7h

    dz7b7h New Member

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    Oops.. :eek: sorry. I've edited the instructions. Thanks for catching that. Like they used to say in school always read through the instructions. HA! Never thought that would come in handy huh? :nice:
    #83
  4. dz7b7h

    dz7b7h New Member

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    Did you do the PI Intake install yourself?
    #84
  5. stangGT97

    stangGT97 New Member

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    haha yeah, who knew? lol

    Yes I did the PI intake install myself. I was very meticulous about it but there is always that possibility that it is messed up somehow. The only work I have not done on my car yet was the spring install (and tire mounting, obviously). Thanks for the update
    #85
  6. dz7b7h

    dz7b7h New Member

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    Did you feel any gains from the swap?
    #86
  7. stangGT97

    stangGT97 New Member

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    it's been a while, but I do remember feeling a moderately harder pull above 4000. Now, I didn't do the cams which was a mistake, that would have helped solidify the gains... and the full headswap would be even better. But for the amount of effort and what it cost, it was well worth it!

    If you plan on doing the intake, I would highly suggest installing PI cams or aftermarket cams to really see good gains.
    #87
  8. Mike97gt

    Mike97gt it doe snot Mod Dude Founding Member

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    the TPS does NOT have to be between .96-.99 please go read my sticky at the top of 4.6 tech..

    this is what was needed on older fords and many other cars.. the TPS voltage at idle needs to be between .53-1.27 and around 4.5 at wot

    the pcm cares a lot more about TP mode in our cars than the real time voltage..

    The way it works in our cars is the PCM KNOWS what it's C/T TPS reading is so even if it's lets say .86 it knows that .86 is C/T so when the PCM sees the volatge rising it knows to enter P/T mode. the rate of this rise is looked at by the PCM to figure out the throttle opening or closing rate. when the voltage is above 4.0 and stops rising the PCM knows your foot is to the floor and enters W/T mode..

    the PCM really only cares about throttle angle rate and tp mode... as long as the voltages are in the spec I told you and if the rises and lowers smoothly when you work the thorrle then your TP is ok.

    Well anyways read my sticky at the top of the forum, I have all the info stright out of the ford PC/ED
    #88
  9. dz7b7h

    dz7b7h New Member

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    Can't find the instructions I used but it was either from BBK or Stangnet or Corral or eh.. who knows.. either way it's just what i've used and haven't had any problems. When I haven't set the voltage within this range I've had issues. maybe my PCM is just really picky. I know she seems to be very sensitive to any change I make no matter how small it seems. Chilton says .9 and others say as close to .98 or .99 as possible.

    I guess so long as you get a smooth voltage change throughout throttle. BTW.. what's ford PC/ED???
    #89
  10. Mike97gt

    Mike97gt it doe snot Mod Dude Founding Member

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    ford pc/ed is fords powertrain control and emmisions diagnostic manual.. it's what we use to diag cars at the dealer. it's writen by ford motor company.

    maybe during adjustemnt you fixed other issues with the TPS on your particular car but by no means does it HAVE to be adjusted.. as long as it's in .53-1.27 at idle and operate smoothly it should be fine. The PCM will learn what voltage idle is and base it's C/T to P/T transition off of that.

    I notice you are messing with the throttle blade adjustment, maybe this is why you had to adjust the TPS on your car.. with the Throttle blade in the factory position your TPS should be within range without touching it.

    BTW.. what is the benefit of doing this adjustments. I am not trying to be a jerk I am just wondering if it ran better when you do this and what the problems were before the adjustment. I am open to try somthing new, but Why mess with the throttle blade so it will run with the IAC disconnected.. it's not supposed to do that, from the factory they have the throttle closed, you are opening the throttle slightly this is why it will run with the need for a bypass of the throttle blade..
    #90
  11. Mike97gt

    Mike97gt it doe snot Mod Dude Founding Member

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    BTW back to the original problem.. I have seen the drivers act up in the PCM on several cars.. In fact another tech at my work is having this issue right now on a 4.6 GT

    the ignition and injectors have drivers built into the pcm that power and activate them.. it's not common but I would look there. This would not be easy for you to diag without scan equipment. codes only tell you so much.. you really need to see live data.
    #91
  12. stangGT97

    stangGT97 New Member

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    ok so that would definitely be a ford only ordeal right?

    As an update, went to Autozone to check if there were any codes, and there were none. Did a vacuum test, a constant 18lbs of vacuum @ idle.
    #92
  13. dz7b7h

    dz7b7h New Member

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    Didn't figure you were. I have a BBK 75MM Throttle Body. It doesn't have the little air hole in the blade that the factory model has. So in order to keep air flowing you have to crack the blade a touch, the equivilant of the factory hole. What I have found with my own car is that throttle response improves significantly when I have it within this range. Anything above this and I get a lot of studdering when accelerating and my car dies a lot. As for below I don't think that I can really say. I read somewhere that anything =>1.00 is telling the PCM that the car is at WOT or at least not at idle. So if this is the case then it closes the IAC and the car doesn't receive the air it needs to run properly.

    I wish I could find that article because I'm by no means a mechanic whereas you are. This is the procedure that I follow only as a result of much research. I know that there is a lot of bad information out there which is very frustrating for someone lilke me with know real technical references. I'm pretty sure I found it on one of these forums and it was written by a guy who ports plenums. Either way I would like to find it so I can point it out to you and others and have it corrected if indeed it is wrong.

    Also, remember that we are dealing with '97s. I understand that the PCMs are different from 99+
    #93
  14. stangGT97

    stangGT97 New Member

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    mike, would a new PCM require reprogramming my keys?
    #94
  15. Mike97gt

    Mike97gt it doe snot Mod Dude Founding Member

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    that anything greater than 1.0 = wot stuff is for the EEC 1 cars like the 5.0's it does not apply to us.. Well atleast thats what ford says. 99 percent of the time the TP voltage at idle is going to be in the .9x range anyways.. but I will keep my eye out for one over 1.0 and will let you know what the T/P mode pid says...

    after reading that you have no air hole in your new TB now I know why you did this adjustment, so it ran like crap with the throttle blade closed all the way.. I will keep this in mind if somebody has a problem with a TB without a airhole.

    yes
    #95
  16. stangGT97

    stangGT97 New Member

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    okay thanks... I'm gonna get an exhaust leak fixed, then if it continues to misfire, I'll send her in to get the ol' anal probe
    #96
  17. Mike97gt

    Mike97gt it doe snot Mod Dude Founding Member

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    well good luck man..
    #97
  18. stangGT97

    stangGT97 New Member

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    thanks for all the help :nice:
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  19. stangGT97

    stangGT97 New Member

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    Another update-

    I had my oil changed and me and the tech inspected the oil - no gasoline could be smelled. It just smelled like 3000mile oil... so I guess that is a good thing. Pulled a few of the plugs and they looked fine, had signs of useage but weren't soaked in fuel or anything. I'm tearing the top of the engine down this week, regasketing the manifold and replacing the coolant tube that runs in the block valley. I'll check for debris in the injectors and any other blockages. New EGR valve is coming Monday to eliminate that as a possibility. I will say though, all in all, the car runs better now w/ synthetic oil in it. I'll keep you all updated on how my work this weekend turns out...

    TGIF! :flag:
    #99

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