my engine is running rough i changed my spark plugs, my wires, and put new coil packs and its still running rough what should i do next ?

Any check engine light?

yes the engine light is on

First thing to do then is get the code read for the check engine light and report back here what it is. You can get it read for free at any parts store (AutoZone, NAPA, Advance Auto etc).
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-Dan
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2012 Nissan Maxima SV Premium • Super Black • Charcoal • VQ35DE • Bose • Factory HID • 5000k LED Int/Ext
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__I n n o v a t i o n__T h a t __E x c i t e s

I bet you have the same problem I had: The Evap purge solenoid at the rear of the car under the filler tube. This is also likely the reason you are having the parallel issue with the gas cap.

When you open your gas cap, does it suck in a lot of air? Are you having any trouble pumping gas? Those were further signs I had problems. The unit is about $40 at Advance and takes an hour or so to replace.

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Russell (Rus or Rusty)
White 2000 SLE - 161k Miles
Current Mods - Transgo Shift Kit, 180* Drilled Thermostat, NGK TR55 & Belden Plug Wires, Suspension Energy Endlink Upgrade, "Stock" 12-Way Power Seats, "Stock" Heated Seats, "Stock" Homelink GDO, Cleared Corners, Pins & Dealer Badge Removed, 2002 56I Center Console, Dash Trim, Steering Wheel and Shifter Swap, Auto-Dimming RV Mirror, Pioneer AVH-P4000DVD MP3/USB Headunit w/ Steering Wheel Controls and iPhone Music Interface, Hood Protector, Gutted Airbox w/ K&N Filter.
Mods in Progress - SSEi Inflator with Stock controls, Chrome "Swoopies" (Have rims, need tires)
Future Mods - Viper 5701 Remote Start with Smart Start and 35% Window Tinting

i did get it checked and the codes are p0420 and p0440

yes i do have check gas cap light so if replace that part that should do the trick and what is the name of the part

Clean the filler neck real good and make sure the cap is tight and has a good seal. Check all the rubber hoses for any leaks.

If you are going to try the vent solenoid, it is Gm part number 21994122.

But I would be patient and try the filler neck and verify the new cap doesn't help.

If it throws a lean cylinder code like mine did, the vent may be worth a try. Unless you want to throw $40 at it and see what happens.

_________________
Russell (Rus or Rusty)
White 2000 SLE - 161k Miles
Current Mods - Transgo Shift Kit, 180* Drilled Thermostat, NGK TR55 & Belden Plug Wires, Suspension Energy Endlink Upgrade, "Stock" 12-Way Power Seats, "Stock" Heated Seats, "Stock" Homelink GDO, Cleared Corners, Pins & Dealer Badge Removed, 2002 56I Center Console, Dash Trim, Steering Wheel and Shifter Swap, Auto-Dimming RV Mirror, Pioneer AVH-P4000DVD MP3/USB Headunit w/ Steering Wheel Controls and iPhone Music Interface, Hood Protector, Gutted Airbox w/ K&N Filter.
Mods in Progress - SSEi Inflator with Stock controls, Chrome "Swoopies" (Have rims, need tires)
Future Mods - Viper 5701 Remote Start with Smart Start and 35% Window Tinting

where is the filter neck located

Where the gas cap screws on.

What is the other thing I need to check before buying that part

Mahki,
Have you read anything I've posted?

You listed TWO codes you had. I gave you the information you needed for those two codes and would've led you to the cause instead of you randomly ripping things out of the car and replacing them...

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Retired Bonneville Owner and former GM Tech:
2004 Pontiac Bonneville GXP: Black/Ebony *SOLD*

Summer Toys: Combined 827 RWHP / 877lb/ft RWTQ
2004 Pontiac GTO: Impulse Blue Metallic/Black/M6: lots 'o mods, 415 RWHP / 405lb/ft RWTQ!
2006 Cadillac STS-V: Light Platinum Metallic/Light Gray/A6 - Spectre CAI, Magnaflow exhaust, Speed Inc. tune, 412 RWHP / 472lb/ft RWTQ

Daily Drivers:
2019 Chrysler Pacifica Limited: Mommy's new RGC
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2007 Chrysler Town & Country Limited: Sold to neighbor
2009 Pontiac G8 GT: L76, Sport Red Metallic
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1999 Chevrolet Suburban: Sunset Gold Metallic - Daddy's winter beater and plow truck