Adjust the fuel/air mixture, ensure you have an unclogged air filter/air cleaner.
We need to know the year, make and engine to help you.
The year, make, model and engine size would help us answer that one for you.
You replace them - you do not fix them!
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.
advance the timing a little.
You don't have to.
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.
To fix a 1988 Nissan Pulsar running rich, start by checking and replacing the air filter if it's clogged, as this can restrict airflow and lead to a rich condition. Next, inspect the fuel injectors for leaks and clean or replace them if necessary. Additionally, test the coolant temperature sensor and oxygen sensor, as faulty readings can disrupt the fuel-to-air ratio. Finally, ensure that the engine's vacuum lines are intact, as any leaks can also contribute to a rich mixture.
If the fuel is running too rich in a car, it would be a good idea to adjust the EFI or Electronic Fuel Injector (carburetor). It would also be a good idea to make sure that all of the air cleaners and oxygen sensors are clean and functioning properly.
Your civic could be running too rich because you used bad gasoline. It could also be running rich if a spark plug needs replaced.
gas