if the isu had quit, most likely it was killed by overamperage draws, i.e. old plugs, wires, cap, rotor and coil. the bigger the gaps, the more power required. all that extra umph the tired coil needed to fire the engine came from the icu. look carefully at the coil where it meets its mounting bracket. if you see white spots, the coil is bad. that happens 'cuz the plugs get left in too long and the gaps open up, which draws more amps and work on the wires, which then, there is more juice arcing through the cap from the rotor. i'd look at that stuff real close. good luck, chuck.