Help me create the "Surging Idle Checklist"

Discussion in 'Fox 5.0 Mustang Tech' started by jrichker, Apr 10, 2005.


  1. 87_stang

    87_stang Member

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    OK guys, last night I re-cleaned the IAC and MAF sensor and also took my dremel to the IAC and opened them up together a little bit like mentioned toward the beginning of this thread. I went about 1/8" in so a little air could get between the two holes. I then fired it up and it idled great so I went and picked up my cousin and we just cruised town for about 30 minutes just to hit all the stop signes and stop lights that way I could keep an eye out on the idle. SO far it is working great! Thank you very much to everyone who has helped out by throwing out ideas for me and everyone else with this problem.
     
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  2. WhitePony93

    WhitePony93 New Member

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    I've been through this checklist over and over. My car has a hanging idle problem. With the IAC unplugged, it will idle down to around 800 RPM, but ends up around 1100 (at best) after I drive it. Also, any time I'm rolling with the clutch in or in neutral it's closer to 1500-1800 RPM's(IAC unplugged). My computer throws no codes, everything is cleaned and functioning properly (IAC, EGR, O2's, Baro sensor, TPS, MAF,VSS). I even broke down for the first time in 5 years and took my car to a shop and had them give me a diagnostic. They said sensors checked out ok , there was a vacuum leak, beween the head and lower intake on the passenger side. I had already torn it down to the heads just days before. I tore it down again, being extra careful to follow proper torque procedures. It still runs exactly the same, and I can't even think of any more areas that could even cause a vacuum leak. What should I do? I'm out of ideas.:nonono:
     
    #222
  3. jrichker

    jrichker StangNet's favorite TOOL SN Certified Technician Founding Member

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    Did you replace the lower intake gaskets or just re-touque them?

    There have been instances where the gaskets have slipped out of place on installation and caused leaks.

    My favorite trick that saves time and effort is the stay in place gasket. Be sure that you scrape (don't use a wire brush) all the old gasket material off, then clean all the surfaces with acetone or MEK.

    When the surfaces are clean, use weather strip adhesive on the head to manifold surface. Also use the weather strip adhesive on the side of the gasket that mates to the head. When you are done, the head surface and the gasket surface that mate together will have weather strip adhesive on them. Follow the instructions on the tube or can and when it gets tacky, press the gasket down on the head.

    Clean the area where the rubber rails mount to the block in front and in the rear with more acetone or MEK and do the same trick with the weather strip adhesive that you did to the heads.

    Coat the rubber seals and the gasket area around the water passages with lots of Blue Silicone gasket sealer and put it together. Bingo! no leaks, and no gaskets that shifted out of place.

    If you reuse the injectors from your old setup, a repair kit is available from most auto parts stores if needed. Coat the injector body "O" rings with oil before you use them and everything will slide back together. Take the other advice you got here and run with it.

    Fuel injector seal kits with 2 O rings and a pintle cap (Borg-Warner P/N 274081) are available at Pep Boys auto parts. Cost is about $2.74 per kit. The following are listed at the Borg-Warner site ( http://www.borg-warner.com ) as being resellers of Borg-Warner parts:

    http://www.partsplus.com/ or http://www.autovalue.com/ or http://www.pepboys.com/ or http://www.federatedautoparts.com/

    Most of the links above have store locators for find a store in your area.

    Use motor oil on the O rings when you re-assemble them & everything will slide into place. The gasoline will wash away any excess oil that gets in the wrong places and it will burn up in the combustion chamber.
     
    #223
  4. BK_CAULEY

    BK_CAULEY it's built for speed not longevity, woman

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    i got one for yall

    when i first crank my girlfriends 1989 gt on the first crank it does its normal 12-1400rom start up and when the rpms come down from the start up it dies. try to crank it again and it does fine. we did this like 25 time in a row. we crank it on time drove it around for about 10 minutes shut it off and it did its dying thing again. let me calrify it a little bit. 1st start cranks then dies 2nd start does fine 3rd dies 4th fine agian and it has done it consecutivly and isnt putting out any codes. any idea's?

    P.S.- if any body has seen my threads i started i disconnected the battery while the car was still running:nonono: and it started surging then it just up and quit now i have problem stated above. but hey without careless people where would :SNSign: be?
     
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  5. WhitePony93

    WhitePony93 New Member

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  6. WhitePony93

    WhitePony93 New Member

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    I pulled the intake tube and covered the idle air hole and it now idles. The throttle body itself seems a bit worn out, there's a lot of up and down play in the blade. Do you think the throttle blade is allowing too much air to pass, making it impossible to bring the idle down far enough with the screw?
     
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  7. jrichker

    jrichker StangNet's favorite TOOL SN Certified Technician Founding Member

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    That is a possiblity. Check the throttle butterfly for a hole drilled it it. Ford used the hole as a means to allow a calibrated airflow to control idle. They would insert a plastic plug to change the size of the hole if it was too big.
     
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  8. Cougar5.O

    Cougar5.O Founding Member

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    The TPS being below 1V makes no sense from the ECU point of view.

    Any setting between 0.8 - 1.1V will be seen as "0" my the ECU.

    I don't know where or how this rumor started, but it is not supported by the code in EEC-IV.
     
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  9. Cougar5.O

    Cougar5.O Founding Member

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    Sorry, it makes no difference if the TPS is above or below 1V at idle, so long as it is not below 0.5V or above 1.2V within the ECU. This means that a measurement of 0.8V - 1.1V will leave you WAY within the acceptable range. The ECU zeros to whatever voltage it sees at closed throttle, so it doesn't matter where it is. If it is outside of the range I mentioned, it will throw a code and behave badly.
     
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  10. jrichker

    jrichker StangNet's favorite TOOL SN Certified Technician Founding Member

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    Site me a reliable source for the above information and I will gladly make changes.

    My personal observation has been that the idle speed increases slighly as the base TPS voltage increases.
     
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  11. WhitePony93

    WhitePony93 New Member

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    I actually have that hole completely plugged now to give it an idle at or around 800 RPM'S:lol: . It's like too much air is able to squeeze around the T.B when it's closed. The blade actually slides up and down revealing a gap below or above it. A new throttle body seems to be in order, now the question is whether or not to get a 65mm from Ford Racing. Will I see any improvement with the minimal mod's I currently have, or will I be wasting my money and time? Keep in mind that I have no planned future modifications of the motor itself(H/C/I, Power adders, etc.)
     
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  12. OonDeanisS

    OonDeanisS Founding Member

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    When i turn my car on, it stalls once or twice and bounces from 1500 to as low as 200rpms before it gets warmed up then it stays at either 1000, or 1500 sometimes. Which of my many sensors do you guys think this is? I put on a new tps, but never calibrated it because i dont know how, but it did this before that anyway.
     
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  13. joel5.0

    joel5.0 New Member

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    J.....this is from a write-up I did on the TPS adjusting myth, the quotes within the article are from the Ford GUFB Strategy document and has also been verified with "tests" I've done in SD and MA systems, including SN95's that allow the access to the parameters via the Datastream option......There are 3 parameters:

    Throttle Pos ClsdVolt = used to id minimum TP value and is reset every time you turn ignition on
    Throttle Pos Mode = CT for Closed Throttle, PT for Part Throttle and WOT
    Throttle Pos Volt = real time value of TPS signal

    Anytime the system detects an increase of .04vdc over the minimum TPS value recorded initially, the idle will increase because the system id's a part throttle condition and switches to a different IAC control strategy. Reason why you have to reset the system by turning the ignition off and recheck the setting when the throttle stop screw is used, as the base idle procedure calls for.

    In addition, if such a setting needs to be so precise, it would go against the benefits of having a computer controlling EFI.....or saying
    "EFI is better over a carburetor setup because it provides the capability and flexibility to self adjust for changes in temperature, altitude, load, etc, etc......but the throttle position?" or......"they (Ford) provided an EEC system capable of dealing with everything but, the TPS variability normal, and expected, in any 3-wire variable resistor component?"......if that was the case.....what about the other sensors?....

    Let us know.......:)
     
    #233
  14. jrichker

    jrichker StangNet's favorite TOOL SN Certified Technician Founding Member

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    Joel5.0: Your information on TPS settings has been incorporated into the main post, and I have given you credit as the authoritative source for the information.

    I am not sure about the source of these comments, and I am also not sure about what you were trying to say. All the sensors have production tolerances and so does the computer and its input circuitry. Ford made a best case attempt to compensate for variables in sensor values and computer sensitivity. Most of the time, the variables fall within limits and everything works fine. Sometimes the shift of a sensor towards the limits upsets a computer whose hardware input sensitivities are also at or near the acceptable limits. The result is often a car that runs flaky one day and great the next.
     
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  15. TENGRAM

    TENGRAM New Member

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    the idle speed is likely to raise when you raise TPS voltage with the engine running. this is because you have just shifted it into part-throttle mode. after turning the car off and restarting, the new "base" value for the TPS is recorded and the idle should be back to normal.

    as evidence for the falsity of the TPS ".99999" myth, i offer this excerpt from an internal Ford document that was originally intended for their engineers:

    [​IMG]
     
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  16. joel5.0

    joel5.0 New Member

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    And appreciated indeed.......the point I'm trying to make, and the source for the comments, is that the TPS is a non-adjustable device, it's a pass/fail, or G-NG (Go-NoGo) variable the system is capable to provide for w/out problems, as long as the operating window (no failure codes) is complied with otherwise, the problem usually lays elsewhere.

    If you look at the strategy, the systems identifies TP state as -1, 0 or 1....-1 being the CT state (minimum reading within .5vdc to 1.19vdc) now, base idle could be set mechanically to 700 rpms and a TPS value of .7 vdc, which would be the same as 700 rpms and a TPS value of 1.09 vdc....anything less would make a carburetor setup gain the upper hand.

    My apologies if it was interpreted negatively, that was not my intention...you have provided details regarding the EEC-IV system, and the proper procedure to eliminate the guesswork out of solving problems, that it should be duly acknowledged......I do.....:flag:
     
    #236
  17. vristang

    vristang Advanced Member

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    Man, these last couple of posts have been great!

    I have seen my car run differently after setting the tps, but that was because the tps was originally out of range, over 1.2v



    While the GUFB can be found on many tuning sites, I have posted it on my site to make it more accessible.
    http://www.freewebs.com/vristang/GUFB.pdf

    It is long, and can be a tough read sometimes...


    jason
     
    #237
  18. leathernotch

    leathernotch New Member

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    High Idle

    After head install, of iron gt 40's. Car idles at 800 cold once she warms up the car doesn't go below 1400, revving causes the idle to stick and it takes awhile to come back down. Vacuum when the car is cold (800to1000) is about 10 or below. Went through top-end and replaced all gaskets. No change. Why would the car idle correctly when cold?

    The car idled at 1400 before we went through and replaced all of the intake gaskets and adjusted valves when we finished she idled the same no change same rpm at 1400 when she is warm. So it has to be another issue
     
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  19. jrichker

    jrichker StangNet's favorite TOOL SN Certified Technician Founding Member

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    You definitely have a vacuum leak with 10" of vacuum at idle. I have seen cases where the lower intake manifold gaskets have slipped out of place. This creates a vacuum leak in the lifter valley that is almost undetectable by most normal means.

    Check up the fuel injector seals when you replace the gaskets. If the injector plastic pintle cap is missing, the O ring can slide down into the intake manifold.

    My favorite trick that saves time and effort is the stay in place gasket. Be sure that you scrape (don't use a wire brush) all the old gasket material off, then clean all the surfaces with acetone or MEK.

    When the surfaces are clean, use weather strip adhesive on the head to manifold surface, and on the side of the gasket that mates to the head. Follow the instructions on the tube or can and when it gets tacky, press the gasket down on the head.

    Clean the area where the rubber rails mount to the block in front and in the rear with more acetone or MEK and do the same trick with the weather strip adhesive that you did to the heads.

    Coat the rubber seals and the gasket area around the water passages with lots of Blue Silicone gasket sealer and put it together. Yea! no leaks, and no gaskets that shifted out of place.

    If you reuse the injectors from your old setup, a repair kit is available from most auto parts stores if needed. Coat the injector body "O" rings with oil before you use them and everything will slide back together. Take the other advice you got here and run with it.

    Fuel injector seal kits with 2 O rings and a pintle cap (Borg-Warner P/N 274081) are available at Pep Boys auto parts. Cost is about $2.74 per kit. The following are listed at the Borg-Warner site ( http://www.borg-warner.com ) as being resellers of Borg-Warner parts:

    http://www.partsplus.com/ or http://www.autovalue.com/ or http://www.pepboys.com/ or http://www.federatedautoparts.com/

    Most of the links above have store locators for find a store in your area.
     
    #239
  20. leathernotch

    leathernotch New Member

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    Tell me more about what the O-rings could be causeing. Could they cause the Vac leak w/ out a gas leak? Could I not see a rise in idle w/ the brake cleaner?

    I also rechecked the F/P and it was at 50 w/ vac off so I broght it down to 40 and did not see any change. Is that odd.

    Could this be the IAC causeing everyting. Because the idle does stick when reved for at least a few seconds at 2000 before droping down to 1400.
     
    #240

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