> belch out thick black lib-ownin' ball-crushin' smoke, damaging their own engine in the process.
The black smoke belching is caused by a fuel rich air mixture that leads to incomplete combustion and is pumped out of the engine as a burning cloud of smog. While this can cause problems with carbon build-up in the combustion chambers, it's not especially difficult to clean that out before the engine suffers permanent damage. Most often the worst case is fouled spark plugs, which are wear items meant to be replaced at regular intervals.
The real damage occurs in the exhaust plumbing, typically rendering the oxygen sensors inoperative and cooking the catalytic converter. However, a common way to induce black smoke is by hardwiring the oxygen sensors to report the engine needs more fuel, so it's not like the oxygen sensors were typically working anyway.
Likewise, in many parts of the country where this sort of "coal rolling" is common, it's also common for the catalytic converter to be forcibly removed from the vehicle and pawned off for the platinum mesh inside by a couple meth heads looking for their next fix, which has the side effect of preventing it from being damaged. The missing portion of the exhaust pipe is frequently repaired by welding in a straight pipe, allowing the black smoke to flow more freely while also making the exhaust notably louder and adding the scent of immediate global warming (note: this is pretty much super illegal in most states).