Hey all,

After the last autocross, well, the next day, my Miata started running really poorly. At cold start/idle there is a very aggressive stumble. The engine also does not rev until about 1/4 throttle, even then, very misfire-like - almost stalling. Once things are warm it is totally fine. Before I go throwing parts at it or spending a ton of cash on labor to find the issue... any ideas where to start besides the basic spark plugs, etc? Similar experiences? Hoping I can amateur-mechanic my way out of this. I haven't looked at it closely yet, waiting for the weekend. No CEL.

I found one of the two coil packs at the rear of the motor was loose, tightened it and no difference. Nothing else feels or looks loose, no spark arcing, frayed wiring, etc. Car was perfect the day before. Last tune up was only 10k miles ago.