Normally no spark from just one coil is due to the coil assembly itself but since you already tried a new one, I'd suspect a broken wire between it and the Engine Computer. That should be detected by the computer and it should set a related fault code. Since it hasn't done that, you might suspect a problem inside the computer itself. It's more likely you'll find a corroded terminal in a connector, or a stretched terminal. The best way to find those is to unplug the connector right at the computer and make resistance measurements for all three circuits. If they all read about the same, suspect the computer. Be careful when sticking meter probes into the terminals because that's the most common way they get spread, then they don't make good contact with their mating terminals.
You can also use a scanner to command the computer to fire each coil without cranking the engine. If all of them fire when requested, that proves the computer, its control circuitry, and the coils are working. The top suspect then would be a cracked flex plate. Usually they won't just spin freely; they can shift position just enough that the crankshaft position sensor doesn't read some of the notches in it that tell the computer which coil to fire and when.
Wednesday, December 12th, 2012 AT 1:43 AM