Tom Mazz/CT

Having trouble with code P1399 - Random misfire. I also get 0301, 0302, 0303, 0304 codes. Have replaced plugs, wires, cap & rotor. Also ran two treatments of injector cleaner. Cleaned up battery ground and ground to body and engine. Removed egv valve and cleaned - everything looks clean.

The car seems to run normal except sometimes at idle it will run a bit rough and CEL will flash....trip the codes. If I give it a little throttle the CEL light will stop flashing.

Car has 165K miles on it.

Tom

madnad

Wow that is what describes my problem too. I am chasing a p1399 on a 99 Civic HX auto myself. With all four cylinder miss fire.
Have changed out the spark plug, wires, dist cap, rotor, coil and fuel filter. Two treatments of fuel injector (gumout variety) so far. New battery and terminals. Cleaned out the EGR passages (for rough idle issues), caused an air leak but was able to patch it up. Even did a cursory compression test which passed. Injectors are firing fine.
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.
I did have to replace 1 Qt oil over two weeks recently but I don't any black smoke or any drips.
It's fun and frustrating trying to get this figured out.