My car seems to be eating coils, and I'd like to have MT's input before I throw another set of coils on there.

Two weeks ago my car (2001 VVT running MSLabs MS3) started misfiring after a cold start while I was tuning the warmup enrichment. I went back to the stock ECU, found the misfire was from cylinder 2, swapped the coils and the misfire went to cylinder 4. I ordered two new Spectra brand coils off of Rockauto, replaced them and she fired right up. I swapped back to the Megasquirt, took her for a spin and noticed some misfiring at high engine speed/load. I pulled over to check some things in tunerstudio and it started misfiring at idle. I went home, did some reading, and increased the dwell to 4ms where I had trouble, and it was better. For about a mile. Then it got worse... increased dwell to 5ms and barely made it back home. In the span of 5 miles it seems my car has killed another set of coils.

Spark plugs are a little worn, but the gap was right at 0.044. Spark plug wires were cheap ones off rockauto, but less than 15k miles old. The coils were not hot when I stopped, both were 140*F compared to the valvecover at 170*F.

What should I check to see why my car has suddenly developed a nasty coil addiction? I did not change anything related to timing or spark until the car developed these misfires.

 

I know very little (read:nothing) about it but I know you can blow the coils switching the ECUs. Something about having the coils connected and not the ECU or vice versa. I was told to remove the negative battery terminal before messing with them to avoid this.

 

 

Don't assume aftermarket coils are fine. Can't say your coil dwell setting didn't ruin it, but once I replaced a bad coil with an aftermarket coil from O'Reillys in a pinch. A week later, O'Reilly coil was dead. This was with a stock ECU. I bought a genuine mazda coil and never had an issue again.

 

Personally I would never change failing coils without changing plugs as well.
If your plug is fouled, spark energy has nowhere to go. This spark energy can easily destroy the coil windings.
Might be interesting to dissect the broken coils to see how they broke.

 

Spark plugs were clean and there was no fouling at the electrodes.

My guess is that the starting difficulties I had stressed the original coils too much, as the default dwell timing was 8.0ms and I was cranking for a looooooooooong time. The new coils, being cheap, didn't last long either.

The problem appears to be solved by switching to junkyard LS coils and sequential ignition. I just put 50 miles on it last night without any hiccups.

 

Unless otherwise noted, I wouldn't run any of the LS coils with 8msec of dwell either. My LS2 / D585 coils max out around 5msec, depending on voltage. Any more and they have a propensity to prematurely fire, which is a great way to do bad things to a combustion cycle.

 

Of course not... I didn't just wire them up and hope for the best with my old settings

I took my dwell settings from Savington's post here in the LSx coil thread. Mine are wired and set up for sequential ignition to make use of that data. I don't think it would work well in a wasted spark setup since that effectively doubles the frequency seen by the coil, and as you say, these coils are apparently known for random firing at higher engine speeds.

250 miles on them since the swap, and all is still good.