Close



Results 1 to 7 of 7
  1. #1

    Default 1986 gt unmolestede

    i f got the idle surge problem. replaced all sensors .no codes in the computer . the more i do the worst it runs .this is not my first 5.0 .this one has got me stumped. bought this gt from senior gentlemen, 126000 clean. the more i drive it and work on it the worst it runs, chang ed coolant sensor,air sensor,plugs , tps, checked for vacuum leaks, surges and dies. hold the rpms about 3000 rpms and you feel it shudder like misfire. no codes though. replaced plugs black like to much fuel. smells like its running rich. any thoughts would be grateful. also replaced idle control.

  2. #2

    Default 86 gt unmolested

    i f got the idle surge problem. replaced all sensors .no codes in the computer . the more i do the worst it runs .this is not my first 5.0 .this one has got me stumped. bought this gt from senior gentlemen, 126000 clean. the more i drive it and work on it the worst it runs, chang ed coolant sensor,air sensor,plugs , tps, checked for vacuum leaks, surges and dies. hold the rpms about 3000 rpms and you feel it shudder like misfire. no codes though. replaced plugs black like to much fuel. smells like its running rich. any thoughts would be grateful. also replaced idle control.

  3. #3

    Default

    It is something the computer can't sense. Quick bet would be plugged converter... The more it runs the worse it runs. Use a temp gun and while running, measure temp in front and in back of the converter. If the front is hotter, it is plugged.

  4. #4
    FEP Super Member erratic50's Avatar
    Join Date
    Dec 2016
    Location
    Nebraska
    Posts
    4,575

    Default

    Ideas
    1 - bad rotor in the distributor. Don’t care if it’s new or old — look at how it makes contact at the center. I’ve had new right out of the box jump around because of bad quality. I run Motorcraft only now. Look for any indication the rotor is hitting the outer contacts on the cap too. Spray down the inside of the cap with WD40 to remove any moisture while you are there

    2 - bad cap ..... check for cracks and indicators that the rotor has ever hit. Corrosion on the plug wire contacts is a big one too — especially for the crappy Ford Racibg 9mm wires I’ve ran into a few times

    3 - I’ve had the seals in a distributor start allowing oil up into the ignition stator in the bottom of the distributor .... ran like CRAP. Check for any oil residue or moisture here

    4 - a marginal coil wire. I’ve burned several off over the years. Usually the go to crap at the center connector on the distributor

    5 - bad coil. Maybe? I’ve had the same coil for 1/2 million miles but some have reported could going bad. Mostly it’s replacement coils that go bad or are bad out of the box though. That brings up another one —replacement parts quality is all over the place on these cars and often BAD. Only replace a part you KNOW is bad ..... you might have fresh out of box wrong or bad parts adding to your mess

    6 - where is the fuel pressure while all of this is happening? Harbor freight sells a cheap gauge kit that works

    7 - When is the last time you’ve cleaned the throttle body. Look for muck and carbon crud on the back side of the throttle body blade

    8 - id open the ECU and look for leaking capacitors. They are getting to be a lot more common due to age on the computers. Or swap the ECU if you have another one.


    i like the converter idea too. Loosen up the exhaust flange and see if an exhaust leak improves the situation as another test if you don’t have a temp gun
    Last edited by erratic50; 12-30-2018 at 02:17 PM.

  5. #5

    Default

    Yeah, I have had a coil behave strangely, not that bad but close. I would do that nice list above. In order.
    1984.5 G.T.350 5.0 CFI AOD Convertible (TRX package, loaded)
    K&N filter in a 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, dura grip (both Yukon)
    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)
    AOD rebuilt with a 6 clutch direct drum, Koline steels stacked with 8 clutches, Kevlar band, superior shift kit, new torque converter. --Everything else stock and fully functional.

  6. #6
    FEP Member
    Join Date
    Dec 2012
    Location
    Jacksonville, NC
    Posts
    102

    Default

    My bet is somewhere in the distributor. The module likes to go bad because the dizzy sits right in the valley and heat soaks. It's failed on most of the foxes my friends and I have had.

    I've also had bad luck with the under $100 parts store distributors. Literally never gotten one to work right, always spitting and backfiring. Actually cost me a year of driving the first '86 I resurrected because I assumed the bad misfire couldn't have been a new part, replaced a bunch of other sensors and wiring to no improvement, then ran out of money because of (at the time) college kid budget. Then it happened again with my '89.
    Last edited by sm41; 01-02-2019 at 12:27 PM.
    '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

  7. #7
    FEP Power Member
    Join Date
    Oct 2004
    Location
    Moyock, NC - (Hampton Roads)
    Posts
    1,093

    Default

    Since you said it smelt rich, i would definitely take the advice above.
    one thing i have run into twice -- fuel pump rubber hose in the housing. fuel pump runs fine. car will idle, but once i gave it gave - car would stumble or cut out. fuel pressure gauge proved it. it was only getting about 20 psi instead of about 40.
    what happens is - the rubber hose that connects the pump to the housing gets cracked/split due to age/ethanol, etc. so half of the gas is spitting back in the tank while you are only getting half of it in the actual fuel rail.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •