Car either misfires or hessitates when i accelerate but if i hit the gas slowly it will not why would this be fixed code 12 and reset now have no flash codes comeing on used to have 4 5 9 12 please help

Throttle Body Relearn:
After replacing the throttle body, it's crucial to perform a relearn procedure to ensure proper communication between the new components and the car's computer.
Here are some methods to reset the throttle position sensor (TPS):
OBD2 Scanner:
Use an OBD2 scanner compatible with your car model.
Look for the throttle sensor reset feature in the scanner.
Follow the scanner's instructions to reset and calibrate the TPS.

Accelerator Pedal Method:
Turn the ignition to the ON position (without starting the engine).
Push the accelerator pedal down fully for about 20 seconds.
Release the pedal slowly and turn off the car.
Start the engine normally and check if the situation improves.

Fuse Removal:
Locate the fuse box (details in the owner's manual).
Remove the fuse related to the throttle body (leave it out for about 10 minutes).
Reinsert the fuse.
The throttle body sensor should reset.

Driving the Vehicle:
Drive the car on the highway at speeds over 40 mph.
Accelerate and decelerate slightly.
Repeat this process to allow the sensor to reset.
Additionally, there's a helpful YouTube video that specifically describes the relearn procedures after replacing the throttle body and the throttle position sensor (TPS) .

Check for Other Issues:
Ensure that the ignition coils, spark plugs, and front oxygen sensors are in good condition.
https://youtu.be/ZNxXM75zJOw You Tube

Accelerator pedal position sensor needs testing.

Check your spark plugs.

fuel filter

Just got a Brand new fuel pump and fuel filter and now my car is smoking and when pushing gas it hestitates

Sounds like a misfire..either maybe a bad coil..or a simple tune up wires and plugs..If it feels like a ""fish bite"" when accelerating slowly up a hill..then its usually in the ignition system..Also look for codes..Is the engine light on or flashing..that indicates which cylinder

I hope I'm wrong but I think your torque converter is failing. Sorry, Gary

when my cars do this I check the fuel supply first.....should be a small filter near the throttle body somewhere that could be prob. then check electric/fuel related items. there are several different items with these symptons, nearly always related to fuel....go to a good websight like autozone repair guide for help....also a haynes or chilton manual available at parts houses will save you lots of bucks----i never take my cars to a garage...this is general info, but i hope it has helped...

HI, i have the samme problemeon my mustang gt 2006
idid hevriting ,plug chek wires , and the probleme was the valve was sticking on the guide ,we change the head , and now it is very jood, good luck
it was misfiring whit no code