I have a Nissan Maxima 2002 3.5 engine. Check engine light has been on for a while had it diagnosed and it said cylinder 6 misfire. looked it up within he last month I have had someone replace the spark plug, I replaced the single ignition coil the light went out til the next morning. the car has been horrible on gas when I go to accelerate it feels like the car is pulling and not to mention when I slow down and then go to accelerate it struggles. and the shaking in the car when idle but in drive. I went to one place they changed the coils around and I was able to drive for about 22 miles and the like came back on. I finally took it to another place that same day and they did a tune up and changed the single fuel injector and my light went out. drove a full drive cycle and then some and the light had stayed out. I was able to drive 238 miles that's 4 days of driving for me. check engine light came back on and the idle shaking gas mileage everything is worse I have even smelled sulfur, gas and other smells inside the car at random times. the gas was just once and recently. diagnosed it at home and now it says cylinder 5 misfire. I was thinking of just having all my fuel injectors changed but then I was thinking after doing research I may have to have my fuel filter and pump changed too. I don't know what to do. I always like to go to the mechanics and let them know what they need to do. I am a little skilled on knowing what the problem is just most things I can't do myself. any suggestions or has anyone had this problem. I love my car and have already put in a little less than half of what I paid for the car into the car in the last month and have only had the car for a year. I have even used seafoam and zmax to try to clean the injectors. Please help me.

 

What are the exact codes popping up?

Did you use OEM parts?

Are the other spark plugs clean?

 

the first code was P0306 fixed that now it is P0305 All the spark plugs were just changed this past weekend. the ignition coil I replace was the one I looked up on an auto parts store website for my car.

 

It is highly unlikely that the spark plugs are the problem. The check engine light does not come on for spark plugs. And don't waste your money on the fuel pump and filter, either.

Your problem is most likely the ignition coils, possibly the fuel injector.

 

Read this:
http://www.nicoclub.com/FSM/Maxima/2002/

Replace spark plugs with oem nissan parts. Replace the ignition coil with oem nissan parts. You can buy oem parts at Courtesyparts.com. Buy yourself an OBD II scanner (try innova 3130). Do not use any injector or fuel cleaner because vQ35DE engine have an electronic throttle.
Spark plug 2,4,6 are in the front bank (near the radiator) can easily access, while sparkplug 1,3,5 (near the firewall) needs the removal of intake manifold (around 4 hours job, cost around $400-500 ,better off doing it yourself) I replaced all my sparkplug with oem nissan platinum, and oem ignition coil, I did it myself.
Good luck

 

^
While OP is in there change the valve covers!