For the last few weeks my car (99) has been horribly misfirng above 3k rpm and >50% throttle. It threw a soft code (CEL flashed but did not stay on) a little while ago, and when i went to check the codes today i got a 5-5 or no problem/fault detected. Do I have to check for a soft code as soon as its thrown, or should it stay recorded in the ecu? I'm guessing this is either a coil or knock sensor problem, but without the ecu's help, im having trouble narrowing the problem down. My next course of action is going to be to check the resistance of the ignition coils.

any help would be appreciated.

Adam

 

Unfortunately, if its not stored and you get an 0505 code, chances are you won't get the code until it happens again. I would do what you just suggested and check for resistance.