I have a 2003 350z and I’ve had a problem with the car hesitating around 2k then backfiring on deceleration. The problem stops once the car is fully warmed up. I had a P0132 and P0152 code so I replaced the upstream O2 sensors and the codes are gone but the problem is still there. If it helps I have a cold air intake as well as high flow cats and a tomei cat back. Any help would be much appreciated.

 

When did this start happening? I could be wrong but iirc aside from the sensors it could be a faulty wire or running too rich. Someone else hopefully can chime in as I haven't been around this platform in quite some time.

 

Double post

 

Seems like the cold start program isn’t running and the engine thinks it’s warm when it’s not. The symptoms indicate lean run. Check to see if mag sensor is clean. But make sure the water temp sensor is functioning. Might be two. 1 for th gauge and 1 to tell the ecu what the water temp is. Ie. To control the cold start program.

 

Agree with this. Sounds like it's lean. Could be electronic (temp sensor, MAF sensor, etc...) or mechanical (injectors, pump). If you've got the cash, put it on a dyno with a wideband. Should prove to be lean.