I've been having trouble with spark breakup under boost since going to a COP kit (using Denso Yaris coils). One of the coils eventually cracked and fortunately the vendor replaced them, but the 2nd brand new set of coils are still misfiring.

If I change back to my stock coils, the car runs perfectly The COP vendor believes there is a wiring issue in my car somewhere, rather than a fault with the COP kit, but I'm struggling to find it.

I can get continuity for the power and earth pins on both plugs for the stock loom, so they seem OK. What I can't get is continuity for the ECU signal wire from either plugs in the loom back to the 2 pins at the ECU plug (10 and 23 for Evo 7). I've tried this with IGN ON and OFF, but not sure if continuity is possible at all doing this test? Any tips how to check these wires from the coils back to the ECU, or anything else to try and track this down??

Car is running NGK BPR8ES gapped to 0.6mm (23.6 thou) running about 23psi on 93 octane.

 

gap your plugs down to .020" and see if the misfire continues

 

Thanks for the reply. I've gapped the plugs down as low as .21.6" (0.55mm), but made no difference. I don't see how plug gap is the problem when stock coils work fine at 0.023" anyway? My understanding is a COP lets you run a bigger gap, so it should be more than happy at 0.023"?

Was hoping someone could chime in and confirm how to correctly test the ECU signal wire from the COP plug back to the ECU, as I'm worried I've got a fault there somewhere since I haven't been able to get continuity.

 

If your stock coils are working fine then it's not the wiring

when you say it's breaking up, do you mean it's misfiring / phantom knock up in the high RPM? if so, have someone check the tune. if you're self tuned it could be an issue with the tune as well

what COP and what coils are you using?

 

Your only partially correct in your statement-- in general a cop will allow bigger gaps but under boost is a different story and you have to reduce gap to fire the plugs consistently, the higher the boost the more resistance to jump the plug gap.

Now onto the wiring, I had a prob with one of my cop coils as well, traced it back to the wire harness plug on the rt side of the cop. The pins didn't always seat so I had a random misfire.. worth a check.

 

Interesting... but what if I'm getting voltage drop or something though due to a wiring issue? Is it possible that would show up in the COP kit and not stock coils, since the COP needs more voltage? Or not at all?

Yes the symptoms are misfiring under heavy load around 4-5K rpm. Again, not sure how it's tune related if it pulls cleanly to redline on stock coils? It is self tuned and AFR's/timing are fine. The one part of the tune which could be causing it is the dwell settings, but I'm using the recommended settings with the dwell reduction factor zeroed out as per one of the threads that MrFred started on here. I've tried a few different dwell settings, but it misfires regardless.

 

OK, but I'm not running a lot of boost really. Only 23psi, which isn't heaps for an Evo and I wouldn't have thought would need such a tiny gap with COP kit?

I was expecting to find an issue with one of the plugs/pins like that, so I'll keep looking. The lack of continuity to the ECU still has me worried, so was hoping someone could confirm that test should work and there's no trick to it. All I did was put a paperclip in the ECU signal wire plug at one of the plugs in the loom at the engine, attach the alligator clip to that end, then probed the ECU plug with a pin (both from the back when plugged into the ECU and from the front with the ECU plug pulled out). Couldn't get anything...

 

Just thought I'd update this thread to say I resolved the issue. Had an auto electrician check out my wiring to the 2 coil plugs and he found a little bit of inconsistency with the voltage going to the coils.

Rather than spend lots of time trying to track down the voltage issue in my loom, he hard wired the voltage/earth wires at the 2 coil plugs directly to the battery via a relay that triggers the power wire when the IGN is on. This fixed the issue straight away - no more misfires on the COP kit with Denso coils

 

Glad i found this. I've been having this same issue since doing my own COP kit in my Evo 6. Been so frustrating.
As you described, worked fine with stock coils but missing under-load with the COP.

I've tried grounding the earth wire on both coil clips and still, re-crimped the pins in the clips as the stock wiring looked shagged but still missing. Even bought a couple new coils to try. Pulling over and swapping to see any difference.

I started to wire up my own dedicated power relay to the coils. After reading the issues you've had I'm looking forward to having it solved.

 

What does the misfire sound like? Does it happen only in boost or all the time? If it happens only in boost and sounds like a machine gun, you've got a bad ignition coil and swapping them won't do anything, you'll need to use a known good one to swap around and see which one gets rid of the issue so you know which coil is bad

 

Made my coil relay and its working perfectly. Engine light stopped flashing at higher RPM too..

 

Man I’m having the same issue switched to cop and car runs like crap. Any schematic on the wiring? That would be a great help.