If the carburetor has an adjustment screw for the lean/richness you can adjust it there.
If the air cleaner is dirty or clogged replacing it might take care of the problem.
If not, you will probably have to rebuild the carburetor.
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.
Thats could be one of two things; your engine is running rich or moisture vapours from a fairly new engine, which is perfectly normally. My advice is to have a licenced technician have a look at it.4mgk5
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.
Adjust the fuel/air mixture, ensure you have an unclogged air filter/air cleaner.
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.
Sounds like you have a faulty thermostat. Its nothing expensive on hard to replace.
P0172 = System to rich (bank1). Year, make and engine would help us help you better.
Check your vacuum lines this usually the cause for a surge in engine speed when idling or running.
Check for worn rings, or running a very rich condition Fuel mixed in the engine oil is never good, it impairs the oil's ability to lubricate the engine, so whatever the problem turns out to be, fix it sooner than later, it'll be cheaper in the long run.
It is normal for a carburetor to "suck air" when you are starting the engine or while the engine is running. You should stop the engine before repairing the carburetor for safety reasons.