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Thread: Surging 84 5.0

  1. #1

    Default Surging 84 5.0

    Hey everyone,

    This is my first post here. I recently required my grandfathers 84 Mustang GT Convertible. It runs but has issues. The main issue Im having is a surge when I put it in park. For example, I start it, everything seems fine. I drive it, everything seems fine. However, when I get back to the house and put it in park, the engine surges to about 1500rpm, stays there and will not come down. Has anyone else had this issue or know how to fix it?

  2. #2
    FEP Power Member
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    Auto would make it CFI. Start with checking the codes. Mine was doing it as well and I found a code for bad purge valve. Easy to check. Not sure if that was the problem but it went away for a while. I don't drive mine often enough.
    Fox Body/3rd Gen MCA Gold Card Judge
    84 SVO 24K miles, 85 Mclaren Capri Vert. 84 GT Turbo Vert.
    88 Mclaren Mustang Vert 20K miles, 89 Mustang LX Sport Vert,
    03 Mach 1 7900 miles, 74 Mustang II, 69 Mustang, 67 Mustang, 14 Mustang CS/GT,
    15 F150 FTX Tuscany, 16 F250 Crewcab, 67 Tbird 47K miles

  3. #3

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    Yes, go get a cheap code reader for obd1 at AutoZone and check the codes before you do anything else. I have some suspicion of what it could be as well, but codes first.
    1984.5 G.T.350 5.0 CFI AOD Convertible (TRX package, loaded)
    K&N filter in stock dual snorkel
    GT40 heads, Edelbrock 3721 intake, MSD 8456 Dist., MSD 8227 coil
    Comp cams XE254H, hypereutectic pistons
    Hooker Super Comp Shorty Equal Length Headers
    catted BBK H-pipe, full custom duals
    Maximum Motorsports caster/camber plates and strut tower brace, 3.73 rear.
    Ford Performance Springs, Firehawk A/S 225/55r16 on LMR TRX r390 wheels (street)
    Federal 595 rs-rr 245/40r17 and 255/40r17 on OE cobra r wheels (race)
    Everything else stock and fully functional.

  4. #4
    FEP Senior Member rodster's Avatar
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    The dreaded surge.... unfortunately the codes for an 84 aren't as good as today. EEC - IV I'm guessing?

  5. #5
    FEP Power Member
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    Actually EEC-3
    Fox Body/3rd Gen MCA Gold Card Judge
    84 SVO 24K miles, 85 Mclaren Capri Vert. 84 GT Turbo Vert.
    88 Mclaren Mustang Vert 20K miles, 89 Mustang LX Sport Vert,
    03 Mach 1 7900 miles, 74 Mustang II, 69 Mustang, 67 Mustang, 14 Mustang CS/GT,
    15 F150 FTX Tuscany, 16 F250 Crewcab, 67 Tbird 47K miles

  6. #6
    FEP Senior Member rodster's Avatar
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    That's worse....

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