Sporadic Misfire With Cd Ignition Box

Discussion in 'Fox 5.0 Mustang Tech' started by viper_dude_06, Nov 17, 2013.

  1. Hey guys my friend has a 1993 Lx which has been converted over to Carb. We just recently installed a Summit ready to run distributor to get rid of the stock ignition box that is meant to be used for carburetor. Its a new distributor that was never used, we just had it packed away SUM-850303 is the part number. Its not produced anymore. http://www.summitracing.com/parts/sum-850303/overview/

    The problem that we are having is that when the distributor is hooked up to a Summit CD Ignition Box the car misfire extremely bad between 2500 and 3700 rpm. The box we are using is and older Summit Ignition Box with out the built in Rev Limiter that the newer style boxes come with. The box has had very limited use. It was packed away for a while as well.

    If we disconnect the Box the car runs fine throughout the rpm range. The car did run better with the Ignition Box on it, other than that bad rpm gap that we had.

    What would cause this. Would it be the vacuum advance, and if it is why would it do it. I hooked the box up to my 1987 EFI setup and I get full rpm band without any problems so I know the box isnt bad. Any help would be appreciated. Thanks
  2. Ive seen issues like that when the magnetic pick up wires were backwards. Not sure if its possible with your setup, since it looks like you have a 3 wire mag plug. You can usually see that with a timing light hooked up, as it will have a real sporadic light pulse at times, if thats the case.
  3. Keep in mind that a lot of the Summit brand stuff is re-badged from Pro comp electronics. I've seen a host of problems with their distributors. I had to modify the weights to get the full advance out of the distributor in the last one I installed for a guy. I would take the top half to the dist. apart and see that everything mechanically is working properly. Also try disconnecting the vacuum advance and just run the mechanical advance as that will be good enough!
  4. The plug that your talking about liljoe07, plugs into an extension set of wires. From that extension I hook it to the box like I would normal to the coil. I have a RED wire that goes from the distributor to the keyed RED wire on the box, then I have a GREEN wire that goes from the distributor to a WHITE trigger wire that goes to the box, and a third BROWN wire that just connect straight to chassis ground coming from the distributor as well. If I dont have the box in place the wires from the distributor go to their respective places. The RED goes to POS side of coil, and GREEN goes to the NEG side. Heres the install instruction that just show a normal hook up to the coil. The distributor doesnt have a magnetic pic up. Any other ideas of what it could be?

  5. 84Ttop I haven't had a chance to pull it apart, but I did read that there was and adjustment screw down in there and the only way to get to it was by pulling the top half off like you said. Maybe thats all I need to do. The vacuum advance moves like it should if I apply vacuum to the distributor with the car off and the cap off. I can see the arm move back and fourth as it should. With the vacuum advance disconnected, it just lowers when it starts misfiring. So instead of misfiring at 2500 rpm it starts at 1500 rpm.