My 8 has been running fine up until yesterday. I was leaving the movie theater and when I started it, it stuttered some on startup, as in it took three full cranks (normally starts up at this point) but this time it had three more short cranks, sounded almost like hiccups....it's hard to explain. I figured it was a fluke until I started backing out of my parking space. It seems to have a pretty serious misifre under 2k, but as soon as it get's above 2k, it runs fine. The misfire mostly goes away after I've gotten it warmed up and been driving for a bit, so I don't think it's compression. Also, because it's was so sudden, it makes me think it's ignition related, but I'm not ruling compression out.

At idle, The trailing ignition coils are supposed to produce spark at a steady rate, right? I pulled one of my trailing wires off and the spark it's producing is irradic, as is the other trailing spark. I immediately thought "they're failing, replace them" but then it crossed my mind that maybe the ecu tells it when to spark and it isn't just at a steady rate.

Thanks, I kinda feel stupid asking this because I feel like they're bad, but they only have 5k on them, so I hate to just replace them.

Here's what's happening, the periods are sparks:

.... .. ...... ... ... . . . .... . . ........ . . . .

TIA

 

HEI Coil Tester for sure would help diagnose this issue.
Cheap item, like 20 dollars. Easy to use as well

 

trailing coils, trailing spark wires, or at an extreme possibility trailing coil harness wiring/connectors

the engine mostly depends on trailing coils for idle and low rpm engine functions, then it switches to leading coils for power and high rpm


https://www.rx8club.com/series-i-do-...-wires-222641/

 

you should check the plug wire too. the resistance spec is in the FSM, but i think it should be 1-4k ohms resistance, higher = certain coil death.

the wire(s) should also firmly clip onto the plugs, if they don't they need to be replaced.

if the coil is bad, the spark plug should be changed too, unless its almost new.


so the coils in these cars actually work ok, and deliver lots of spark energy, but they are delicate, so if there is a bad wire, or spark plug, it will probably kill the coil. this happens on piston engine cars too, the 90's 626 was infamous for this, the valve covers leak on the plug wires, which kills them, and then ruins the $1000 distributor.

 

I did the timing light test with my buddy's timing light last night and the front most coil was going and so was the rearmost one. The front one only fired about every other spark and stopped for a full two seconds when the engine was revved. The rear one wasn't quite as bad but it was definitely failing. I had a couple extra coils lying around so I just threw em in and it runs great again. Such a big difference in power. Thanks for the help guys