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  1. #1

    Default New to me 86 gt, Couple of issues.

    Hello, I recently purchsed a 1986 mustang. The car had a messed up pushrod when I bought it I've fixed that so the 5.0 sounds great. Still cant get it to idle until warmed up and it runs extremely rich. The car is stock except long tube headers and exhaust. The 02 sensors are installed and hooked up.

    Any help would be very much appreciated.

    Thank you.

  2. #2

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    I would check the vacuum level of the engine. Also make sure there are no major vacuum leaks. Since you don't have a maf, unless its been converted, a bunch of leaks and poor vacuum would make it run like crap.
    Also run the codes for koeo and koer to help determine what's wrong

  3. #3

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    Would a vacuum leak cause the car to run rich?

  4. #4

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    If brain-dead EEC-IV senses things too lean, like with a vacuum leak, yes, it'll add fuel.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  5. #5
    FEP Member
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    Dec 2012
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    My '86 is extremely sensitive to vacuum leaks. The tiny line going to the TAB/TAD controls cracked, and the car would not run at all. Plugged that hole with a nail I found on the side of the road and it ran perfect again. Ripped out all that crap as soon as I got home.
    '86 Mustang GT T-top. GT40P swap, Maximum Motorsports subframe/coilovers, MGW shifter
    (RIP) '86 Mustang GT, T-top. Cipher's old car
    '91 Wrangler. 4.0, 5 speed, 8.8 swapped, locked, lifted, caged
    -Steve

  6. #6
    FEP Power Member Ourobos's Avatar
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    Apr 2008
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    Waikoloa , Hawaii
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    1,879

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    I would wonder why the pushrod was bent.. They don't bend themselves.
    1986 CHP SSP Coupe

  7. #7

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    I’ve checked for vacuum leaks and I could not find one. I’ve also replaced the fuel pressure regulator and it helped but the car still doesn’t want to idle also still burning rich. After a while if I keep revving it and messing with the throttle it’s like nothing is wrong it idles great and runs good. I can only figure the push rod got bent from over revving the engine cause it broke the ball off of the end of the push rod. I can only guess it was overevved and due to valve float must’ve become misaligned with the rocker arm.

  8. #8

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    Name:  FA72F400-4142-404C-B2A3-61E6AFC292EE.jpg
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Size:  39.2 KB yes I found the ball

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