K so i bought a 1998 civic Si with a D15 swap (only the head and block were changed) i have replaced the PCM (or ECU the honda tech called it a PCM) the main relay, spark plugs, and had an oil change. Before i replaced all that minus the main relay, it was fine at first then it started bucking like crazy, the tach would drop to 0 (even though i was in gear and driving) and the engine light would be flashing and i could hear a clicking where the ECU(PCM) was by the passenger footwell. Got an oil change, changed plugs, and ECU and car was a lot better, but still every once in a while the CEL flashes and the car bucks, and then its fine again. this happens less frequently than when i swapped the ECU. does anyone have ANY idea what the hell this could be? cuz it does not store the CEL code, it just flashes and bucks then nothing, back to normal. oh ya, power and fuel economy was BRUTAL before swapping in the new ECU.