We need to know the year, make and engine to help you.
Engine is running rich
If your truck is dieseling or running on, it could be that the fuel is too rich. Try using a lower octane of fuel.
It's running too rich.
The year, make, model and engine size would help us answer that one for you.
It will be smoking black out of the exhaust / Running RICH. Spark plugs will be fouled out/ Black. Replace them if it is running rich. Plugs will not fix your problem. Replace map sensor.
Adjust the fuel/air mixture, ensure you have an unclogged air filter/air cleaner.
my truck was doing the same thing before i had the choke set right, because it was partially closed, making it flood out and run rich
No - you do not need to have the truck running.
You may be running rich. You may also have a gas leak. Check your fuel line fittings for leaks.
I will fix it
You may have a bad catalytic converter. This may also be caused by an engine running rich which is a number of possibilities.
What kind of truck? What is wrong? Diesel, or Gas. Pickup or Large Truck? You need to be more specific. ie; how do you fix a woman? I ned more info.