I just recently purchased a nissan maxima 2002 with 115k. but I am having issues with it already. car drive great but for what ever reason check engine light come up and if I press the gas hard it would kinda choke, also if I drive pass 70 Mph car will stall instill it drop to 60 Mph. please help me. engine codes are P0650 and P0420. I changed the air flow meter but still the samething. please let me know if you guys know how to fix this problem. If I Reset the computer car goes back to normal but then an hour after driving it. the engine light goes back on and the issue comes back.

 

The P0429 says you have a plugged pre-cat (catalytic converter) in bank 1 of the engine. Bank 1 is the side of the engine towards the firewall.

The P0650 says you have a problem with the Check Engine light. I have never dealt with this code, so I don't know what to say about it. The service manual says that when you have the P0650 code and any other code at the same time, the engine's computer (ECU) will go into fail-safe mode, which reduces the power output of the engine.

Read page 455 of the service manual here:

http://boredmder.com/FSMs/Nissan/Maxima/2002/EC.pdf