My 2003 Touring keeps throwing code PO 300
Multiple cylinder misfire detected. I just had all new plugs put in. Mechanic check the voltage on the coils said they were all working fine. Service engine light comes on random and blinking. Car seems to run fine. Sonetines the car seems to have slight idle problem. Maybe mechanic missed diagnosed the coils. Open for suggestions. Thanks Chris

 

P0300 NISSAN - Cylinder Misfire Detected Random Cylinders

Possible causes:

Faulty spark plug
Faulty ignition coil
Clogged or faulty fuel injector
Intake air leak
Fuel injectors harness is open or shorted
Fuel Injectors circuit poor electrical connection
Ignition coils harness is open or shorted
Ignition coils circuit poor electrical connection
Insufficient cylinders compression
Incorrect fuel pressure

Read more: https://www.autocodes.com/p0300_nissan.html

350z plugs need to be gapped wider than many other vehicles. If your mechanic just threw them in without adjusting the gap that could be the culprit. Also leaks in the air intake system can happen if it’s not put back together properly.

I’d start there.