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  1. #1

    Default Continuing CFI issues

    Hi all still fighting a CFI engine. 1985 5.0 Auto. I can not get it to idle or get it to stop falling off every time I give it gas.
    History to date is,
    dropped gas tank and verified it was clean,
    fresh gas,
    new plugs and plug wires,
    new rotor and cap, verified number one piston at TDC and the rotor is pointing to the number one cylinder,
    Replaced EGR valve,
    Replaced TPS,
    Replaced all gaskets and packings on the CFI unit,

    Symptoms have only marginally improved with all this from where I started.

    https://www.instagram.com/stories/mercstang/

    Attached Images Attached Images  
    Scott

    85 McLaren Conv
    84 Capri (parts car)

    2001 F250, 2006 Mustang GT Conv, 63 Herbie The Love Bug Clone

    Looking for a Blue T-Top V8 car with EFI

  2. #2

    Default

    Have checked the 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 intake
    K&N filter in stock dual snorkel
    Comp cams XE254H, hypereutectic pistons
    catted BBK H-pipe, full custom duals
    Maximum Motorsports caster/camber plates and strut tower brace, 3.73 rear.
    Firehawk A/S 225/55/16 on LMR TRX r390 wheels (street)
    Federal 595 rs-rr 225/45/15 on 10 holes (race)
    Everything else stock and fully functional.

  3. #3

    Default

    And the last cfi with that problem found it was plugged cats. After a really really long time trouble shooting.

    http://vb.foureyedpride.com/showthre...42#post1909042
    1984.5 G.T.350 5.0 CFI AOD Convertible (TRX package, loaded)
    Hooker Super Comp Shorty Equal Length Headers
    GT40 heads, Edelbrock 3721 intake
    K&N filter in stock dual snorkel
    Comp cams XE254H, hypereutectic pistons
    catted BBK H-pipe, full custom duals
    Maximum Motorsports caster/camber plates and strut tower brace, 3.73 rear.
    Firehawk A/S 225/55/16 on LMR TRX r390 wheels (street)
    Federal 595 rs-rr 225/45/15 on 10 holes (race)
    Everything else stock and fully functional.

  4. #4

    Default

    Do you happen to have a bunch of carbon on the back side of the throttle body blades? That really messes with things on the CFI and EFI cars.

    pull it off, clean it with throttle body cleaner, and make sure you get a matching gasket when you put it back down

  5. #5
    FEP Power Member gmatt's Avatar
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    Default

    Along with all that has been suggested, check all of the vacuum lines for leaks. The hard lines get brittle and crack. The rubber lines get soft and rot.

  6. #6

    Default

    But first... 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 intake
    K&N filter in stock dual snorkel
    Comp cams XE254H, hypereutectic pistons
    catted BBK H-pipe, full custom duals
    Maximum Motorsports caster/camber plates and strut tower brace, 3.73 rear.
    Firehawk A/S 225/55/16 on LMR TRX r390 wheels (street)
    Federal 595 rs-rr 225/45/15 on 10 holes (race)
    Everything else stock and fully functional.

  7. #7

    Default

    Ok Codes are as follows:

    KOEO Codes
    23 Throttle Position (TP) sensor Signal out of range (I had already replaced the TP sensor before this)

    Continuous Memory Code:
    None
    Last edited by TLB_Nut; 12-22-2019 at 02:27 PM.
    Scott

    85 McLaren Conv
    84 Capri (parts car)

    2001 F250, 2006 Mustang GT Conv, 63 Herbie The Love Bug Clone

    Looking for a Blue T-Top V8 car with EFI

  8. #8

    Default

    Well, that looks ok. But that tp sensor could cause your issue, and it shouldn't throw a code replaced or not. I would see if it jumps around on an ohm meter.
    1984.5 G.T.350 5.0 CFI AOD Convertible (TRX package, loaded)
    Hooker Super Comp Shorty Equal Length Headers
    GT40 heads, Edelbrock 3721 intake
    K&N filter in stock dual snorkel
    Comp cams XE254H, hypereutectic pistons
    catted BBK H-pipe, full custom duals
    Maximum Motorsports caster/camber plates and strut tower brace, 3.73 rear.
    Firehawk A/S 225/55/16 on LMR TRX r390 wheels (street)
    Federal 595 rs-rr 225/45/15 on 10 holes (race)
    Everything else stock and fully functional.

  9. #9

    Default

    Thanks for the help guys,

    I was getting this Continuous memory code before and it came back today. 18 Loss of Tachometer input/IDM circuit failure/SPOUT circuit grounded

    I need to get the correct probes for my multimeter so I can read the TPS.

    So next update is I removed the catalytic converter in case it was clogged and found the mufflers were trashed. So I removed all of it. Ran the car. Still now real change, still will barely idle and can not give it any throttle without it falling on its face. Unless you feather the throttle gently till it gets over 2K. I can not figure it out at all.
    Scott

    85 McLaren Conv
    84 Capri (parts car)

    2001 F250, 2006 Mustang GT Conv, 63 Herbie The Love Bug Clone

    Looking for a Blue T-Top V8 car with EFI

  10. #10
    FEP Power Member gmatt's Avatar
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    Default

    check fuel pressure?

  11. #11
    FEP Super Member xctasy's Avatar
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    Quote Originally Posted by droopie85gt View Post
    I'm glad you soldered it! 9 out of 10 times, if you have a problem and there's a crimped connector nearby, it is the problem.


    See http://vb.foureyedpride.com/showthre...dle-adjustment.

    Do those checks first.

    Then back track thru' the chocklate block connectors.

    two ways.

    Quote Originally Posted by xctasy View Post
    OTC 4460 2-piece Electrical Connector Separator Tool.
    Owatonna Tool Company stuff is very good.






    JA Cook likes to give each clip the Texan shot glass treatment, and soak in mineral terps, then wash out with clean water. Then dry. Then use an Exacto knife to trim the clips so they don't grab so serverly.
    Quote Originally Posted by Basin Motorsports View Post
    I use a small pick set that I have. Nothing fancy.


  12. #12

    Default

    Ok sorry I haven't posted on this continuing issue. While I am trying to sell/trade the car I am still working on the idle issue. I have cleared the codes, cut off the exhaust (replaced with a temp Muffler, no cat). Still won't idle and stumbles and falls on its face if I try and give it gas.

    So I bought a fuel pressure tester. Bingo here is my problem! At engine off but key in the on position there is only 0-5 psi, Start the car and play with the throttle to keep it running, the pressure is a steady 18 psi. I know it should be 39 psi. I have a new fuel regulator on it's way.

    So is my problem, faulty fuel regulator or weak fuel pump? I have a regulator on it's way (it was the cheaper of the 2). Hope it is not the fuel pump, since I wave a full tank and those pump assemblies are pricey.

    I'll keep working on this till I can sell/trade it. Really want it running good again. The car deserves to be back on the road
    Scott

    85 McLaren Conv
    84 Capri (parts car)

    2001 F250, 2006 Mustang GT Conv, 63 Herbie The Love Bug Clone

    Looking for a Blue T-Top V8 car with EFI

  13. #13
    FEP Power Member fgross2006's Avatar
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    I have a thread on my CFI issues too but mine are more about working out the bugs to get it at 100% efficiency.

    You are at the beginning of an arduous process. getting the CFI to run right can be an exercise in frustration. But once you know the things to look for you will know more than most professional mechanics could tell you about the functionality of the CFI set up. I wish i had a dollar for every time a mechanic said "you'll never get to run right, they all run like that". Or "Just put an edlebrock and a holley 4bbl on it and get rid of that crap".

    If your car cant maintain it's idle I would say first you have to physically set that. It's only partially computerized. The ECM will never 'learn' if your settings are way off. Just a run down of what I'd do;

    !. Set the cold Idle at 2100 RPM by adjusting the flat head screw on the left side just under the choke pull down assembly. You Will slightly open the throttle to release the cam on the left side and set it on the highest position. Disconnect and plug the EGR vacuum, the Choke pull-down vacuum and the Dashpot/VOTM vacuum and the fuel vapor purge valve vacuum, that's right in front of the CFI. Also, pull the voltage wire to the choke so it doesnt heat up and move while your working. Start the car and turn the screw until the idle is at 2100 as per your dashboard tach unless you have an external one.

    2 Shut the car off. Test the choke pull down assembly with a vacuum pump. it should hold vacuum. if it leaks down you have to replace the choke pull down assembly diaphragm. they are easy to find on ebay. I found the black rubber one to be superior to the orange one.

    3. Use vacuum pump to apply to the dashpot/VOTM up to 20 on the dial. It can bleed down to 10 in 10 seconds and its OK. If it leaks down faster, or wont hold vacuum its a bad unit and lots-o-luck finding a suitable replacement. Thats what i have been dealing with.

    4. back probe the green wire on the TPS. Remember when you install a new one you have to set the voltage AND when you turn the cold idle screw you affect the voltage setting on the TPS. So after setting the cold idle I always re check the TPS voltage. You should be able to loosen both screws and tilt the TPS both ways while looking athe voltage meter reading. I have read that setting should be between .96 and .98. So I have always aimed for .97. Tighten the screws back up and thump the throttle to WOT and let it go. The meter should go up and drop back to .97.

    5. Set the curb idle on the dashpot/VOTM. get the car running to full operating temp. take it around the block a few times. Park it, shut it down. The steps to set the curb idle are'
    A. start the car and leaving in park, bring the RPMs up to 2000 and hold there for 60 seconds.
    B. At 60 seconds take foot off throttle, wait 15 seconds.
    C. At 15 seconds put foot on the break and put car in drive.
    D. look at the RPMs on the dashboard tach. Should be at 550. For me, just a hair above the second line over 500.

    If the car isnt at 550 you have to adjust the Dashpot/VOTM. Loosen the saddle bracket on the inside end of the dashpot closest to the CFI. You need to turn the worm screw on the outside of the Dashpot to adjust the idle. Clockwise to raise, counter clockwise to lower the idle.

    After making the adjustment, tighten the saddle bracket and re run the process from A through D. Until you get it to 550 RPM.

    Also, check all vacuum hoses. There's not that many so really its not a bad idea to just change them all. the plastic colored lines are delicate and irreplaceable with color coded hoses again. I'd leave them be if you don't need to disturb them, but all rubber vacuum, change them. they are all probably old anyways. Just change them one at a time so as not to mess up the re routing.

  14. #14

    Default

    fgross2006 thanks for the input. I am hating this CFI system for sure, not to mention it also has all the smog crap on it too.

    It seems I do need a Dashpot/VOTM and yeah I can't find one.
    I can't seem to get the probes I have on the TPS, I need to buy different ones, so I can set it.

    I did replace the Fuel Pressure Regulator and idle got a little better but still falls off if you give it gas and dies. Idle when it will idle it hunts bad.

    Fuel pressure oddly got worse. Running at idle or giving gas the pressure stays at 12-14 psi (it is a Harbor Freight gauge, but it was reading higher with other regulator, not much but higher) I know it should be 39 PSI. So I guess that means my in tank fuel pump is weak? and needing replaced, right?
    Scott

    85 McLaren Conv
    84 Capri (parts car)

    2001 F250, 2006 Mustang GT Conv, 63 Herbie The Love Bug Clone

    Looking for a Blue T-Top V8 car with EFI

  15. #15
    FEP Power Member fgross2006's Avatar
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    Quote Originally Posted by TLB_Nut View Post
    fgross2006 thanks for the input. I am hating this CFI system for sure, not to mention it also has all the smog crap on it too.

    It seems I do need a Dashpot/VOTM and yeah I can't find one.
    I can't seem to get the probes I have on the TPS, I need to buy different ones, so I can set it.

    I did replace the Fuel Pressure Regulator and idle got a little better but still falls off if you give it gas and dies. Idle when it will idle it hunts bad.

    Fuel pressure oddly got worse. Running at idle or giving gas the pressure stays at 12-14 psi (it is a Harbor Freight gauge, but it was reading higher with other regulator, not much but higher) I know it should be 39 PSI. So I guess that means my in tank fuel pump is weak? and needing replaced, right?
    heres you go. Grab it before someone else does. the numbers dont match perfectly but I'd bet my life this part will do the trick. I just bought one that had slightly different part number and it works great.
    https://www.ebay.com/itm/NEW-OUT-OF-....c100036.m2109

    That smog pump and all the stuff behind it has to function. Its hard to imagine that it could impact the performance but it does. I had a rough idle last summer. Pulled codes, came up with a TAB not bypassing code. the NOS part I had put in a few years back had failed. i put the original TAB back in, the code went away and the rough idle went away too.

    I have found that the CFI set up runs like a Swiss watch when its all set up right. it runs like a washing machine with ball bearings bouncing around when there's a problem,.

    Take it from the top,

    Check for codes. If they are present, research them or post them here.
    With the car running in park, move the 3 step cam on the CFI to the high step. Set the cold idle screw to 2100. Back probe the TPS green wire after turning the cold idle screw and verify its no higher than .98 volts. Check the vacuum on the choke pull-down. if it doesn't hold vac, replace the diaphragm, Pop in that NOS dashpot and set the curb idle according to this procedure;

    Curb Idle Reset

    This procedure applies to all models that use either Cfi or Efi. All 86-91 models with Efi have a non adjustable curb idle yet this procedure will set the throttle body stop screw to the factory position for the ECU to use as a reference for Curb Idle.
    1. Put the transmission in either Neutral or Park and set the Parking Brake
    2. Start and allow the motor to warm up to normal operating temperature
    3. Connect the Tachometer per manufacturers' instructions (use the dashboards tach)
    4. Place the Air Conditioning in the OFF position
    5. Turn the vehicle OFF then RESTART and increase engine speed to 2000 rpms for all 83-85 models with CFI or 1800 rpms for all 86-91 models with EFI for 1 minute. Then release the throttle and allow the idle speed to stabilize for 15 seconds.
    6. Check if the curb idle speed was obtained by checking the tachometer with the engine at idle speed.
    7. If Curb Idle is too low turn the ignition OFF, turn the Saddle Bracket Adjusting Screw (83-85 CFI) or Throttle Body Adjustment Screw (86-91) one full rotation CLOCKWISE. If its too high, turn the saddle bracket adjusting screw counter clockwise.
    8. Recheck Curb Idle. Adjust if necessary. Re-do the steps if another adjustment is needed.

    I always aim for 1000 rpm in park and 550 in drive. Also, when back probing the TPS green wire I use either a long thick sewing needle or I unfold a thick paper clip. You can push it down into the back of the connector until you feel it bottom out. I use a pair of alligator clips to grab the needle/clip and I clip the ground alligator clip to the CFI.

    I believe the fuel pressure for the CFI should be at 39 but research that one. If you need a new fuel pump I went with a Walbro. Nothing crazy. I think I went with their 155 LPH.

    Heres link to a NOS choke diaphragm
    https://www.ebay.com/itm/1980-85-For...t/223759561077

    Heres a link to a NOS choke thermostat.
    https://www.ebay.com/itm/Carburetor-....c100012.m1985

    These went bad on me and caused all kinds of problems. Cheap to replace.
    Last edited by fgross2006; 02-25-2020 at 07:11 PM.

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