I have a 2003 G35 coupe 6MT with the following mods: Nismo cold air intake, Motordyne copper iso 5/16 spacer, Crawford hi-flow cats, and a stock exhaust. Recently, my passenger side cat blew and my car threw a SES light. Checked code and it was P0011 and P0021. Replaced the car with OEM cats and both camshaft sensors were replaced and O2 sensors were cleaned. Drove the car for a couple of hundred miles and the car threw another SES light - P0011, P0021, and P0030. Then, the car seemed to shudder at idle and occasionally stalled when coming to a stop...

This all happened a week or two before Christmas. Since then, I've driven the car may be 100-200 miles. The strangest thing now is, I noticed that my car isn't shuddering at idle or stalling. Anyone have any idea what may have happened? Was there too much carbon buildup before that my car wasn't functioning correctly and it just needed to burn off? Did my ECU have to relearn the A:F mixture after the O2 sensors were cleaned?

 

what is the P0030 coming up as?
WHat did you clean the O2 sensors with?

P0011 = Cam Phase Sensor
P0021 - Ignition Signal Circuit


Its possible you just needed to clear some crap out. Sounds to me like when you blew the cat the ECU freaked out due to excess back pressure and it made Bank 2 run weird.

Replacing the cam phase sensors with OEM is critical too. I've heard people use aftermarket and continued to have issues.

 

If my memory serves me correct, P0030 is a random misfire code. I personally did not clean the O2 sensors, my mechanic did. Oh, I forgot to mention that even with the new cam sensors the error still came up.... so my mechanic switched them back. Hopefully, my car just needed to re-learn.

 

you have all the mods...did you get a tune like osiris done to your car. might be running lean and that is causing your cats to clog and run lean.