P0300 - Multiple cyl misfire
Po301 - 0304 (Misfire for each cylinder)
p1399 - Manufacturer Control Ignition System or Misfire

I drove my car 1500 miles to the dragon last week, and by the time i got there (700 miles into trip) it was missing slightly at idle. Car still drives fine around town, but has a bit of a lumpy idle. Plugs were replaced around 4000 miles ago, and were all torqued properly in their sockets a few days ago (well after trip). Motor has 84k on it, so i suppose the injectors could be getting a bit dirty.

Any thoughts on what might be causing it to miss on all cylinders, at idle?

Thanks guys...

 

first thing i would check is plugs, spark test each coil. make sure spark is good.
second, check valve adjustment. tight valves will cause misfire and if left tight too long will burn the valve.
3rd if it wasn't just plugs or most likely valve adjustment check injector pulse with noid light. and check all injectors for clicking.

if you have access to a scan tool that can check map voltage. make sure the map sensor voltage is under 1 volt at idle, at full operating temp, no loads on. if one volt or higher, check your valves right away.

 

Had the valve adjustment done by the stealership in February. I'm hoping they didnt f-things up!!!

 

I was getting those codes every couple of days. I did the modified map whack, revving the motor between ~2000-4000rpm while tapping on the MAP sensor with a screwdriver per Billman's method. It had been doing it for ~3 weeks or so, after the method described above it hasn't thrown codes again over the past month.

 

^ Interesting - i'll have to try that one! Maybe i can get the girlfriend to rev it for me while i whack it haha

 

just go under the hood and hit the throttle while you tap it.

 

Find a scan tool with a data list. Erase the codes and then watch the data list to see which ones are really missing. Sometimes the ecu will throw the random misfire when it really is just one missing.

 

are the codes read out as they are stored, or in order of code number?

 

I'm fairly certain its in the order they occurred.

 

I'd pull the plugs and check them for fouling or missing cathodes to start. What plugs are you using?