I think expense is basically the problem.

Cost to replace the catalytic converter, cost for new exhaust pipes, cost to diagnose ignition timing problems. Whatever.

If the car drives and you don’t have the money I can completely understand why someone wouldn’t get the problem fixed. Even if it means they’re burning a 1/3 of their fuel, that’s still less in the short term than the $1500 it may cost to fix it.

It’s insanely rare I get the sense that the person is running really dirty on purpose.

I don’t know what a realistic fairway to fix it is. They’re probably isn’t one. I don’t think fines would work, it would probably just make things worse. Seems like the kind of thing where a little government group to find the worst 0.1% of cars on the road and just get them back to reasonable levels would be a huge help.

But that’s not how we do things.