I don’t think it be a fuse. Same fuse powers all so if it was a fuse, none would fire. I’m leaning towards a signal issue that’s not getting sent from the pcm or a open wire in cyl # 4 harness

 

I wonder what caused the gap to widen to that gap? Weird?

 

That's the thing. You are probably right. I'm hoping for a fuse as that's the easiest to replace. If there's an open wire how am I going to find it without cutting open the insulation...?

 

You and me both. I think that set of plugs was fake. No other reason I can think of. Now the question is, could that specific plug which has the widest gap (although all of them are just about that wide in terms of gap) have caused a wiring issue in coil pack connector 4??

The AEM EMS is obviously working well to the point that it does fire the AP1 coil in cylinder 4 and before this it fired any other new coil until the coil stopped firing while I drove...

 

without opening up insulation, ohm out Or continuity test of individual wire. Measure one end of wire and where the other end is with a Multimeter and see if you get a reading. With the meter if you have a audible one and you test the individual wire itself, it would make a beep sound or display reading In ohms. If there’s a break in that wire, it will display OL

 

i know with heat and cooling can cause the metals to expand over time but not that large unless it’s a crap plug. Only other thing is possibly it was overlooked and forgot to get gap prior to install?

 

That's an excessive gap though. I got rid of those plugs and put my genuine NGK set back in so that's ok.

No need to gap them. Even this fake set looked like a much smaller/tighter gap prior to install.

 

So I did more testing today and might be scared at what I found. Ground wires all seem to be good. I decided to look at the ECU end of the wiring harness so I removed the AEM Series 2 and tried the ohm/continuity test again. There was no continuity at coil pack connector 4 or 3. The only thing present was continuity for the battery voltage (middle and rightmost terminals of the coil connectors). I then decided to connect my stock ECU and do the same test. The very same results as above! No continuity between the ECU control terminal and the middle terminal of the coil pack connectors!! I even switched the ignition on just to see if that made a difference to the test but nope... The same results. 0 continuity (no beep or red light) on the multimeter when I probed the coil pack connectors on their ECU and middle wire terminals.

So what do you think? Physical AEM EMS issue?
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And i could not find any clear wire breaks or shorts but I did not open up the harness. After this multimeter test I doubt that's needed anyway and we can (probably) safely assume that there is no physical wiring problem. I even swapped ignition fuses just in case before doing the test so the fuses are good

 

AEM replied:

"The previous spark plugs could not put the EMS into some sort of failsafe mode. There isn’t one. Bad plugs could damage Coils but not coil drivers within the EMS. Your resistance readings sound within spec old or new. The difference is nil.

No burned wires and all OEM does not really mean much when you are talking about a 20 year old car.

If you can rev out on any type of coil used, it means that the issue is mechanical maybe wiring related in that the plugs on either the coil or the harness may be the culprit".

Note: the good news is after changing out those crappy plugs I can now rev out to 9200 with no hiccups! That being said, cylinder 4 only plays nice with the AP1 coil pack I currently have in it. All other new ones suddenly don't fire when connected there.