Mazda Miata 1999 1.8L - P0300 Fault Code: Random Misfire Diagnosis and Solutions
Hello! I'm experiencing a P0300 random misfire code on my 1999 Mazda Miata 1.8L, which appears occasionally when starting the engine. The car runs roughly for about 30 seconds before returning to normal operation. I've already replaced the spark plugs and ignition wires, and confirmed that the crankshaft position sensor gap is within specifications. Based on these checks, I suspect a faulty ignition coil as the root cause — I plan to test it soon. Does anyone else have encountered this P030 or similar misfire behavior in their 1999 Mazda Miata? Any insights or troubleshooting steps would be greatly appreciated. P.S. My English is not perfect — I'm actively working on improving my writing skills!
I've seen this P0300 code in a 2000 Mazda Miata SE, but only under specific conditions. The car runs smoothly when cold-started (e.g., first thing in the morning or after sitting for several hours). However, if I restart the vehicle after it has sat for 45 minutes to 2 hours, I experience rough idling and a noticeable fuel smell. Once the engine reaches its normal operating temperature, the misfire disappears and the car runs normally. I've already replaced the spark plugs, ignition wires, and installed a new fuel filter. Still no resolution. Does anyone have a reliable diagnosis or solution? I suspect a faulty temperature sensor, but I'd rather not replace parts without knowing for sure. Thanks in advance!