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  1. #1

    Default 84 bird 5.0 idling issues

    Recently bought an 84 5.0 tbird and in order to start it you gotta keep your food on the gas to keep it running, then it evens out, but as it runs it will surge and then just die. Does the 5.0 have an iac valve on the cfi?

  2. #2

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    Sorry I am unable to help you as I have no experience with the CFI but I just want to offer some advice. You can post this in either the V8 powertrain or the General Tech forums and generate a lot more response.
    Liberty once lost is lost forever.

    John Adams
    July 7, 1775

  3. #3
    FEP Senior Member Greywolf's Avatar
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    Just in case you didn't post elsewhere; there IS an IAC valve on the CFI. The V8 guys can probably help you more with it, though.

  4. #4

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    Check for a vacuum leak for the stalling. Sometimes the rod in the iac will stick causing an rpm surge. You can spray with electrical cleaner or replace.

    Sent from my 5017B using Tapatalk

  5. #5

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    Not sure whether the V8 T-Bird uses an ISC motor. The V8 CFI Mustangs do not, only the 3.8s do. The
    CFI V8 Mustang does have a pneumatic kicker, but that's only an on/off deal. CFI does not employ a
    discrete IAC valve like what's used on the SEFI systems.

    First step here should be to pull KOEO (and if possible KOER) codes. The CFI cars use the same EEC-IV
    data link connector and test procedure as the pre-OBD2 SEFI cars, but a few of the code definitions differ.

    In the Mustang V8 CFI, idle speed is controlled by varying the ignition timing. Therefore, the base timing
    setting is crucial to having that system work properly, as is a clean PIP signal from the TFI system. The
    other crucial thing is fuel pressure. CFI in all flavors is very picky about fuel pressure.

    CFI also depends very heavily on a clean MAP sensor signal. The vacuum line that feeds the MAP sensor
    must not have any leaks, and it must be a straight shot, with nothing else teed into it. And do make sure
    the MAP sensor itself isn't leaking. The '84 MAP sensor is also not quite the same as was used on the later
    Mass Airflow SEFI systems. If you need a new one, I would try to find a NOS Motorcraft DY-503 on Ebay
    or the like, or grab a non-leaking one out of a boneyard organ donor.
    Last edited by JACook; 05-08-2017 at 01:27 PM.
    Cheers,
    Jeff Cook

    '85 GT Hatch, 5-speed T-Top, Eibachs, Konis, & ARE 5-Spokes ... '85 GT Vert, CFI/AOD, all factory...
    '79 Fairmont StaWag, 5.0, 62K original miles ... '04 Azure Blue 40th Anny Mach 1, 37K original miles...
    2012 F150 S-Crew 4x4 5.0 "Blue Coyote"... 65 coupe, 289 auto, Pony interior ... '67 coupe 6-cyl 4-speed ...
    '68 Vert, Mexican block 307 4-speed... '71 Datsun 510 ...
    And a 1-of-328 Deep Blue Pearl 2003 Marauder 4.6 DOHC, J-Mod, 4.10s and Lidio tune

  6. #6
    FEP Super Member xctasy's Avatar
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    Some used EECIII right until the end. Its a pure DSIII system with its idle control via the earlier method..

    Including the curliest one...

    http://vb.foureyedpride.com/showthre...great-at-speed

    Quote Originally Posted by Smkn600ctd View Post
    IT PASSED!!!!!!!

    The numbers were flat out awesome....flew right through the dyno smog test. 37 HC 0.01% CO 277 NoX

    Then while idling....it died. Had not died in three days, just the hiccup and lowering idle. While I was there talked to a old school ford mechanic who thought it could be fuel pressure regulator maybe malfunctioning.

    So half the saga is done.......

    Of course, Smkn600ctd like all expense-d out old car owners was thinkin' "its just easier to scrap it and give up" , but the above post is typical of the results you get when you follow the rules.

    Same account from NAVYCAT when he had to smog his White Black Magic Capri....effectively got some old junk yard parts, popped it on his 3.3 I6, and it passed smog.



    There is about 12 years of data from people who have conquered the idiosyncrasies of the speed density EECIII and EECIV CFi.

    The problem wasn't that its brain dead and and a Bit Cee Hiach, but because the guy that championed the SD CFi was a freekin' rocket scientist, and you have to be smart to understand the flags and protocols of the pre Port Injection 2 injector CFi.


    Only Ford would put a crank sensor on a EEC III CFi vehicle....


    Sorry about the awfull diagram...real mix n match.. and this is why non service technichian types had sooo much problems with CFi 5.0
    /Where is the BMAP sensor on my EECIV CFi 5.0? There is none...
    ?Why is there a box under the CFi 5.0 Tbirds seat?.the EECIII is under the seat, the DSIII some other place,
    ?Why can't I find the ISC? There isn't one on EECIII and EECIV CFi 5.0's
    ?Why can't I find the CPS on my EECIV CFi 5.0? There isn't one on EECIV CFi 5.0's
    ?Why doesn't the diagram show tube headers? CFi HO 5.0 and 4bbl HO 5.0's only
    ?Why is there no Primary Light Off Catalyst? There are none on CFi 5.0's...3.8's, 4bbl HO 5.0's only
    ?TPS voltages...changed on most 1982 cars from , except EECIII!
    EECIII and 1980-1981 #E0VE-9B989-AA Ford sensor for Variable Venturi has a 1.6-2.0 volt curb idle between black and green wires
    Later models, all EECIV style all 0.8 to 1.0 volt at curb idle between black and green wires. Except EECIII

    I've spent the last seven years looking for that kinda stuff that just isn't there on 5.0 CFi's because of these sh!++y diagrams.....but at least it gives us something to look at.....







    I'm sure your enjoying this, JA....


    Remember free1986's idle problems...well its was simple...I guess its why people give away CFi cars for free, 5.0 or 3.8...

    Quote Originally Posted by free1986 View Post
    I'm back! I was so mad at this car I couldn't see straight and almost sold or traded it several times. ........

    Right before I parked it, I swapped the intake to cure the broken and rattling heat riser valve.

    I also discovered that someone had taken the intake off before, and the gasket had slipped on the back of the block, which seems to have been the source of most of my oil leak. It may have also been a vacuum leak too. At around the same time I changed the vacuum modulator on the transmission because it wouldn't shift into second gear. All of these combined to make the car run much better.

    Pictures:



    .........


    CFi owners?


    See Eff I care!

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