Couldnt pass up a deal for this 99 Prelude. Have fix all other problems for under 50.00 it now runs. But have ran into a wall. Like everyone else I have the P1399 code for random missfire. Got rid of codes P0301 and P0303 by installing new wires and seating into sockets all the way. Next I will ohm out coil and ICM. Anything else I should try, please let me know thank you.

 

Any updates since your last post.
I am chasing a p1399 on a 99 Civic HX auto myself. Have changed out the spark plug, wires, dist cap, rotor, coil and fuel filter. Cleaned out the EGR passages (for rough idle issues), caused an air leak but was able to patch it up. There is a belt squeal when AC is on so my next move will be to replace the idler pulley. There is a mention somewhere that belt tension can cause random missfire. Anyways, hope this will solve my problems. I have gotten upto 32 mpg but now it is down to 24 -26.