Ignition problems?

[daxjb]

I have a 93 lx with a 302.My motor is missing at 4000 rpm's .It seems to get better when the motor warms up .I checked my voltage at the coil and it's only 10.5 volts.Just out of curiosity i used an engine ground for the negative and i measured 12.5 volts.Seems as if i have a bad ground.I relocated my battery to the back so i ran an 8 guage to the front for the computer ground.Looking at a schematic shows the negative for the coil comes from the computer.I checked the ground at the computer for continuity and it's good.I even tried another A9L to see if the computer was bad and it did the same thing.I know the 2nd computer is good.If anyone can think of anything i would greatly appreciate it.

 

[Black1987Stang]

Yeah the coil ground goes to the computers, it's mixed in with the pip sensor in the distributor which tells the computer to ground the coil and make it spark....so idk if it will serve as a 100% ground....I'm sure Jrichker or Hissin would know....I know I've checked it before but I forget my reading

If you got a MSD 6AL box take out the rev limiter chip, my friend was doing the exact same at 4k, took out the chip and all was good...

 

[fstrbz]

where is all your grounds connected? frame, engine, computer ?

 

[jrichker]

How good are the coil, distributor cap and wires? If you have a spare coil laying around, try swapping it out.