Alrighty then. I'm very new at swapping engines out and am finding myself in somewhat of a rut. I recently purchased a '91 Civic Si that needed a new engine. Luckily i came across a '94 Civic Dx engine and decided to swap it out. The '91 has all the original parts in it except for the engine and distributer. The engine turns over and idles for a short time (5-10 secs) rather roughly. After this short time it either shuts off or backfires. I have tried adjusting the distributer and the timing belt and also replaced the Spark Plugs and wires. I would like to now what the hell is the matter with it and any and all suggestions are appreciated. I suspect I'll probably need a new ECU and Harness but I'm really don't know.