I have been working on an issue with spark on my trailing plugs. The car is difficult to start (must floor the throttle to get it to start) and the trailing plugs foul all the time. I have tested the spark on the trailing plugs and it is a weak orange spark.



The compression is good on both rotors and the only thing not stock is the mazda speed coil overs. I've tried some old plugs (IRE01-27's) that have a smaller gap, this helped it start easier than the new plugs but the spark is still weak.



The plugs are new 7's and 9's, the plug wires are new. The ohms on the coils are within the FSM specs. I have also tried a known working ignitor. None of these new parts have made a difference.



The ground on the upper intake is good and so is the one on the coils. The wiring to the coils looks good visually (no hard/cracked plastic etc..)



I had thought it wasn't an issue with the coils because it would be unlikely for both coils to fail at the same time.



At this point the only other testing I can think of is power to the coils and verifying the ground is adequate. Is there an additional test that can be performed on the coils to verify they are not faulty? What could be causing a weak spark on both trailing plugs?

you don't even need the trailing coils... i ran my car for years with only the leading plugs firing. What does the spark from your leading coil look like?



I have seen coils pass the test according to the manual and still be trash.

The spark on the leading coils is a small blue spark. I will be putting in new trailing coils when they arrive and see if that results in a better spark.



I have since tested the wiring between the coils, ignitor and ecu and all of it is fine.