First thing would be to check for battery voltage at the coil with key ON.
There are 4 wires on the coils plug in(12v and 3 EDIS ground wires), Red wire, usually, should have full battery voltage with key ON.
This voltage comes from the EEC relay in the Power Box(engine compartment fuse box)
Fuel injectors should also have full battery voltage with key ON, this also comes from EEC relay, so check at least one of those as well.
What starts the ball rolling for spark, on distributorless systems, is the CKP(crank position) sensor, on 4.0l it is located on passenger side lower front of engine behind main pulley.
On the crank, behind pulley, is what looks like a gear with teeth, one tooth is wider than the rest, that's matched with TDC for #1.
EDIS-6 module(Ignition control module) is located on the Rad support, this is what the CKP sensor connects to, it is also powered by EEC relay.
When you crank the engine over the CKP sensor sends pulses to EDIS-6 module, which in turn sends pulses to Computer(Power control module, PCM)
The EDIS-6 starts the spark when it sees the CKP sensor pulses, it doesn't need the PCM for this.
PCM starts fuel injectors when it sees the pulses from EDIS-6 module.
If you have any spark at all I would think CKP sensor is OK, bad CKP sensor = no spark at all, never heard of weak or intermittent spark associated with CKP sensor
I would also check voltage at coil while cranking engine, should be no lower than 9.5volts.
New battery voltage is 12.8v
75% life is 12.5v, about 3 years old
50% life is 12.2v, about 5/6 years old, time to shop for battery sale, next cold morning will get you "click, click, click", lol.
Last edited by RonD; 09-02-2014 at 11:24 AM.