Code 1399
 

OK I am throwing a code 1399 which I know is a random misfire, and it always misfires at around 3000-3300 rpm's, I have an F23a1 head with a H23a block and I can't seem to figure out what could be causing this. You never feel or hear the miss fire, car runs smoother and better than it ever has except this, I have changed the distributor, checked the EGR and MAP sensors, adjusted the fuel pressure, any suggestions on what else to try? Thanks for any help!

Re: Code 1399 (TS4L)
 

What ecu you got in there?

Re: Code 1399 (filthy_shovel)
 

Right now the stock OBD2 ECU, not even sure what ECU it is, I plan to convert to OBD 1 and use a P28, but the harness I bought was messed up and I went through it and need to pull some plugs and rewire them. I am pretty sure when I do that it won't catch the miss fires becuase they are so unnoticable but I want to solve it and I am wondering if some more tuning will get ride of it! I thought it might be a lean misfire but I hooked up my wideband and it looks fine so I'm not sure what else to try! The only way we can even get it so we can notice the misfires is if you shift to 5th gear at low rpm's (1500) and give it full throttle, it will begin to misfire at around 2500 rpm's and you can feel it slightly and after about 3200 rpm's it goes away! I just can't think of what else to try, but thanks for any help!