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  1. #1

    Default 86 3.8 CFI running rich/will not idle

    Second time posting about this...

    Still stuck with this issue.

    1986 3.8 CFI. I have to hold the throttle wide open to get the engine to fire up, though runs extremely rich until about 3500rpm, but when I lift off the gas it'll stall out and not start back up until I unplug the injectors.

    I've replaced the fuel injectors, rebuilt the TB, replaced fuel filter and I would not want to keep dumping money into this thing. Though I would like to mention that before we rebuilt the TB there was still fuel being shot into the injectors until I disconnected the battery, this is not an issue anymore as that has been resolved.

    Here are some things I have thought of:
    Timing
    Fuel Pressure Regulator
    TPS
    Idle Air Control

    I would appreciate any advice there is to offer, Thanks.

  2. #2
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    I would start by measuring the fuel pressure at the throttle body.

    Can you clarify this statement:
    before we rebuilt the TB there was still fuel being shot into the injectors until I disconnected the battery, this is not an issue anymore as that has been resolved.
    Do you mean that fuel was leaking from the injectors? I'm not sure how you would have seen fuel going into the injectors themselves. What was done to resolve this issue?
    '89 XR-7 5 Speed
    '95 SC 5 Speed
    '91 Crown Vic P72 351W
    '95 Saturn SW2
    '85 Ford LTD Squire

  3. #3

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    Every time I see a post like this one at this forum (this one, a second time), coupled with the usual and loud sound of crickets, I have to ask... where are all the electronic fuel injection cheerleaders now?...

    The words of the day for your described symptoms are rich and flooding. Anything requiring your foot to the floor for maximum air intake to get an engine started means there's a ton of fuel in and/or going into the engine... ditto with an apparent "clearing up" and running at 3500+rpm... though with a questionable 32 year old good handful of variables like sensors/switches whose function requires verification, a couple miles of wires and vacuum hoses whose integrity requires verification, and a brain (dead) box that may or may not be getting the inputs it requires, or is the fly in the ointment itself, basic function and the application of logic and reason to troubleshoot problems with internal combustion no longer apply... and the tail-chasing and money-dumping could continue until the end of time unless a different approach is taken to attempt to sort these electrical/mechanical excuses for an automobile out. FYI, an inexpensive, basic, simple, reliably and repeatably running, elimination of all said variables, very good running solution for 2+ years now can be found beginning at post #63 in my "build thread" regarding my own 1986 3.8L V6 Mustang...

    http://vb.foureyedpride.com/showthre...d-thread/page3


    In addition to checking the things you mentioned, checking for trouble codes needs to be done for any chance whatsoever at trying to resolve this issue of yours. Though additionally, the MAP sensor can and will fool the system and you, so it's output signal/function is also required to be checked. Something is obviously telling the brain box to open the injectors wide open at seemingly all times, and if the car's going to remain as is, you're going to have to dig in big time and find out what exactly isn't right, by seeing if there are trouble codes, and trying to follow those hints to find out what's wrong... such as sensors themselves out to lunch, wiring continuity compromised (open, short circuit, corrosion, etc.) between sensors and the brain box, vacuum hoses allowing vacuum leaks, etc...

    Trouble code explanations:
    http://vb.foureyedpride.com/showthre...lanations-from

    Sensors testing procedures:
    http://vb.foureyedpride.com/showthre...s-Testing-from


    Good luck with it, and may the hair-pulling and money-dumping be minimized.
    Last edited by Walking-Tall; 07-18-2018 at 07:16 PM.
    Mike
    1986 Mustang convertible 3.8L ---> BUILD THREAD
    1983 Mercury Cougar 3.8L LS
    1986 Ford Thunderbird 5.0L ELAN
    1966 Ford Fairlane sedan 200-6
    1966 Ford Fairlane GT (390ci 4spd)
    1981 Mercury Marquis Brougham
    1980 Capri RS Turbo
    1971 Mustang Fastback
    1974 Pontiac Luxury LeMans

  4. #4

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    Quote Originally Posted by KevinVarnes View Post
    I would start by measuring the fuel pressure at the throttle body.

    Can you clarify this statement:

    Do you mean that fuel was leaking from the injectors? I'm not sure how you would have seen fuel going into the injectors themselves. What was done to resolve this issue?
    By that, the TB would still try to dump fuel into the injectors, with the new injectors coming with seemingly faulty o-rings the fuel had nowhere else to go other than down the side of that injector. All it took was a new pair of o-rings.


    Sent from my iPhone using Tapatalk

  5. #5

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    I have my suspicious about a capacitor in the ECU. Is there anyone near-by that has an old ECU that works with your motor? what are the codes on your ECU box?

  6. #6
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    You can rent a fuel pressure tester at an auto parts store to check the fuel pressure if you don't have one. The MAP sensor test referenced by Walking Tall is also easy to perform. Additionally, you only need a paperclip or other short piece of wire to check for any stored codes in the computer. A check of the voltage of the TPS as it sweeps through it's range wouldn't be a bad or difficult thing to do either. I'd start with the simple/easy/free stuff before moving on to the more complex issues.
    '89 XR-7 5 Speed
    '95 SC 5 Speed
    '91 Crown Vic P72 351W
    '95 Saturn SW2
    '85 Ford LTD Squire

  7. #7

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    Quote Originally Posted by KevinVarnes View Post
    You can rent a fuel pressure tester at an auto parts store to check the fuel pressure if you don't have one. The MAP sensor test referenced by Walking Tall is also easy to perform. Additionally, you only need a paperclip or other short piece of wire to check for any stored codes in the computer. A check of the voltage of the TPS as it sweeps through it's range wouldn't be a bad or difficult thing to do either. I'd start with the simple/easy/free stuff before moving on to the more complex issues.
    I believe my father has a fuel pressure gauge somewhere over here so we'll go through everything soon


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  8. #8

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    You can rent a gauge free from places like AutoZone.
    1984.5 G.T.350 5.0 CFI AOD Convertible (TRX package, loaded)
    Hooker Super Comp Shorty Equal Length Headers
    GT40 heads, Edelbrock 3721, Comp cams XE254H, hypereutectic pistons, catted BBK H-pipe, full custom duals. 3.73 rear. CS5 225/60/15 on 10 holes.
    Everything else stock and fully functional.

  9. #9

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    Why do we think the fuel pressure is bad?

    Codes. Codes, codes. Run codes. The more you mess with it without running codes, the worse it will be. Seriously, 2 minutes and a paperclip.

    Cfi engines are super picky with vacuum leaks, as well as the map sensor. With how much has been messed with and replaced, hopefully vacuum leaks have been checked.
    2 1986 cougars (both 4 eyed and 5.0)
    1 1987 cougar

  10. #10

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    I'm having a similar issue. Mine will start fine, and run great at first, then when at temp, after driving a bit, it'll stall while stopping and sometimes as I'm slowing down to turn. I've replaced plugs, and even went as far as putting an edelbrock 3in pro flo filter on it thinking it'd give more air flow. As long as I'm pushing the throttle, it runs great. I have 84 lx 3.8. My next guess is to replace fuel filter, thinking it might be partially clogged. It ran fine up until a month ago. It was a barn find. Older couple, so all original with 91k on motor so not tampered with. Just has become frustrating because I love driving it but can't safely.

  11. #11

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    Check codes and see if it giving you PIP codes.
    1984.5 G.T.350 5.0 CFI AOD Convertible (TRX package, loaded)
    Hooker Super Comp Shorty Equal Length Headers
    GT40 heads, Edelbrock 3721, Comp cams XE254H, hypereutectic pistons, catted BBK H-pipe, full custom duals. 3.73 rear. CS5 225/60/15 on 10 holes.
    Everything else stock and fully functional.

  12. #12

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    Check the resistances of the air charge temp sensor and the coolant temp sensor. The former went bad on my CFI 5.0 car and caused some issues similar to what you describe. You will need a table of temp vs resistance.

    and as others above have stated read the codes, that will help a lot.
    1985 LTD LX original owner

  13. #13

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    I have also grounded the hell out of my engine and many of the intake related ECT/EVP/MAP codes went away. But still, go to autozone and buy the 30 dollar code reader. See if it is giving you PIP codes.
    1984.5 G.T.350 5.0 CFI AOD Convertible (TRX package, loaded)
    Hooker Super Comp Shorty Equal Length Headers
    GT40 heads, Edelbrock 3721, Comp cams XE254H, hypereutectic pistons, catted BBK H-pipe, full custom duals. 3.73 rear. CS5 225/60/15 on 10 holes.
    Everything else stock and fully functional.

  14. #14

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    Finally got around to running codes and checking the TPS with the old man.

    Let's start with the codes:
    17
    27
    28
    21
    54
    5
    13
    The only one that matched up with the code list was 54: something to do with a temperature sensor which makes no sense. Now I know I probably ran codes wrong or mis-counted or whatever, first time for the old man and I for a long time.

    TPS: checked voltage with the TPS. Read 1.8-2.8 when closed, 5.3 wide open.

    So if you go back up to my first post I mentioned that it ran extremely rich up to 2500-3000 rpm, then cleared up and ran fine at those speeds. That's probably our main issue? It makes perfect sense to me but I'm unsure whether it's the only issue.


    Sent from my iPhone using Tapatalk

  15. #15

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    Are those koeo koer in order?
    1984.5 G.T.350 5.0 CFI AOD Convertible (TRX package, loaded)
    Hooker Super Comp Shorty Equal Length Headers
    GT40 heads, Edelbrock 3721, Comp cams XE254H, hypereutectic pistons, catted BBK H-pipe, full custom duals. 3.73 rear. CS5 225/60/15 on 10 holes.
    Everything else stock and fully functional.

  16. #16

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    Tps should be around 1v at idle. Pretty much anywhere from like .6-1.1v is fine. 2 is way, way too high.
    2 1986 cougars (both 4 eyed and 5.0)
    1 1987 cougar

  17. #17

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    Btw, tps should never go over 5v's. Not sure you had a good reading.

    Signal reference is the 5v from the computer, tps runs through the computer and is grounded back through the computer. Mine usually tops out at 4.5v or so no matter what.

    Litterly the whole computer should even have 5v's and the tps will always be lower.
    2 1986 cougars (both 4 eyed and 5.0)
    1 1987 cougar

  18. #18
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    Hey guys. Frankenstang's father here.

    All codes pulled were KOEO, but the reader I have is old and i don't think it's working properly. I'm going to order a new one today hopefully.

    We checked TPS voltage yesterday. I'm getting 5v from the EEC, with throttle closed the return was bouncing between 1.5 and 3. I agree that it was definitely too high. We swapped with another used TPS and closed throttle voltage dropped, but was still high. I need to check the ISC to make sure it is retracted when we are testing. This could be another issue.

    EGR is functioning correctly, but i did not check the position sensor yet.

    Most of the vacuum lines are the hard plastic that Ford liked to use in that era. I may go through everything and replace with rubber, just to eliminate the chance of any leaks there.

    Also need to check the MAP, but they buried that behind the overflow tank.

    Looking forward to getting this going, but don't want to spend much on it as we have a swap planned for hopefully next year.

  19. #19

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    Pull your phone out record a video of codes and upload it to YouTube that way you can go back and double-check the codes if you need to and putting it up on YouTube lets us help you
    2 1986 cougars (both 4 eyed and 5.0)
    1 1987 cougar

  20. #20
    FEP Super Member gr79's Avatar
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    Auto stores sell plastic line in rolls.
    Check all rubber fittings and connectors.
    Electrical sensor pigtails and wiring too.

    Replacing just the plastic prob cheaper than multiple rubber hose length cuts, connectors, multiple id's needed.

  21. #21

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    Code reader came in today. Time for some accurate codes. (These are in order) (K/ON E/OFF)

    Quick note. Had to ground the harness to receive codes.
    51: ECT sensor circuit open/ECT indicates -40 F
    22: MAP/BP sensor out of range during self test
    68: RPM not within Self test range
    23: TPS out of range
    54: ACT sensor circuit open/ACT indicates -40 F
    31: EVP voltage out of range during Self test

  22. #22
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    Default 86 3.8 CFI running rich/will not idle

    Iím curious if the fact that we had to ground the diagnostic connector (jumper wire from single terminal connector to battery) plus having so many different codes coming up is a sign of a a ground issue that needs to be investigated further.

    Beyond that, itís time to start reading and finding the charts to check the temp sensors and the MAP. I may go ahead and order the factory emissions manual. This also gives me an excuse to use the breakout box Iíve been hanging on to for the last 20+ years.

    Since the TPS was already suspect and they are cheap we will probably just order a new one and replace it.

    Once we fix whatever issues there are related to the codes we got we can check for the KOER codes and deal with those as necessary.

    Any and all input from you guys will be much appreciated. At the rate we are going we will have this figured out just in time to put the car away for the winter.


    Sent from my iPhone using Tapatalk

  23. #23

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    Repeats, from post #3:

    ... if there are trouble codes, and trying to follow those hints to find out what's wrong... such as sensors themselves out to lunch, wiring continuity compromised (open, short circuit, corrosion, etc.) between sensors and the brain box, vacuum hoses allowing vacuum leaks, etc...

    Trouble code explanations:
    http://vb.foureyedpride.com/showthre...lanations-from

    Sensors testing procedures ( "the charts" ):
    http://vb.foureyedpride.com/showthre...s-Testing-from
    Mike
    1986 Mustang convertible 3.8L ---> BUILD THREAD
    1983 Mercury Cougar 3.8L LS
    1986 Ford Thunderbird 5.0L ELAN
    1966 Ford Fairlane sedan 200-6
    1966 Ford Fairlane GT (390ci 4spd)
    1981 Mercury Marquis Brougham
    1980 Capri RS Turbo
    1971 Mustang Fastback
    1974 Pontiac Luxury LeMans

  24. #24

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    Went though and tested the sensors brought up from the scan yesterday.
    Recap:
    51: ECT sensor circuit open/ECT indicates -40 F
    22: MAP/BP sensor out of range during self test
    68: RPM not within Self test range
    23: TPS out of range
    54: ACT sensor circuit open/ACT indicates -40 F
    31: EVP voltage out of range during Self test

    Note: We did not test the TPS as we had already pointed that out to be faulty.

    Other than that we would still appreciate any advice you guys have to offer!

    Code #51 test:

    • Coolant temp: 76 degrees fahrenheit
    • Resistance: 25.06 kilo-ohms



    • Reference

      • Circuit 354 (LG/Y)
      • Pin #7

        • Reads 5 volts
        • Resistance: .7 ohms

          • Continuity OK

    • Return

      • Circuit 359 (Bk/W)
      • Pin #46

        • 5.7 volts
        • Should be reading 2.6-3.0 volts based on temp
        • Resistance: .7 ohms

          • Continuity OK

    Code #22 test:

    • Reference

      • Circuit 351 (O-W)
      • Pin #26

        • Resistance: .7 ohms

          • Continuity OK

    • Return

      • Circuit 359 (BK-W)
      • Pin #46

        • Resistance: .8 ohms

          • Continuity OK



    • MAP

      • Circuit 358 (LG-BK)
      • Pin #45

        • Resistance .8 ohms

          • Continuity OK

    • VREF Test

      • Read 5.0 V OK

    • MAP/BP Test:

      • 15 in vacuum

        • No change in voltage (5.0 volts)

          • Should read 1.51-1.61 volts

    Conclusion: MAP sensor may be faulty.
    Part Number: E6PF9F47981A
    Code #54 test:

    • VREF

      • Circuit 357 (LG-P)
      • Pin #25

        • 5.1 volts

          • Resistance: .7 ohms

    • Return

      • Circuit 359 (BK-W)
      • Pin #19
      • No Voltage @ Pin #19
      • Voltage @ in #28, 46, 1
      • 5.7 V

    • ACT Sensor

      • Should read 37-24 kilo-ohms
      • Read 25.68 kilo-ohms

    Conclusion: Check circuit 359 (BK-W) possible short in return.
    Code #31 test:

    • VREF

      • Circuit 351 (O-W)
      • Pin #26

        • Reads 5.06 volts
        • Continuity OK

          • Resistance: .6 ohms

    • Return

      • Circuit 359 (B-W)
      • Pin #46

        • Continuity OK

          • Resistance .6 ohms

    • EVP

      • Circuit 352 (BR-LG)
      • Pin #27

        • Continuity OK

          • Resistance .5 ohms

    • EVP test

      • 2.052 kilo-ohms @ no vacuum
      • .366 kilo-ohms @ 5in vacuum
      • 351 ohms @ 10in vacuum
      • 326.0 ohms @ 12in vacuum

    Conclusion: Possible Faulty EVP
    Part Number: E43F9G428A1


  25. #25
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    If anyone has any questions or comments please let us know. I feel like we did a pretty thorough check of everything.

    As of right now Iím looking at ordering a TPS, MAP and EVP to hopefully clear some of this up. The ACT check and ECT check have me scratching my head a bit.


    Sent from my iPhone using Tapatalk

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