The problem was the concept of a direct-drive turbine in a car in general. Emissions are fairly clean; free of all the currently "harmful" components besides Nitrogen Oxide. That was later reduced by what is effectively EGR; which isn't as bad of an idea in a turbine as in a piston engine because the exhaust gas can be injected into the intermediate or even exhaust turbine stages instead of the compressor; which won't reduce power.
Anyway, the reason the turbine car was a failure is because it's a bad idea in general; especially using a primative turbine using 1960's technology. Turbines are only efficient at their full rated power; any low-power condition and they're abysmally inefficient. They are also unable to rapidly change speeds; which is a major reason as to why they're unsuited to power automobiles. Modern military turbines have improved significantly; the F404 being able to spool from 60% thrust to full power in just 4 seconds, but a 1960's era turbine, especially a primative one that remained affordable for use in a car would take orders of magnitude more time. Turbines also have enormous volumes of very high temperature exhaust gasses.
The ideal use for a turbine in a land-based vehicle would have a gas-electric powerplant; meaning having the turbine running constantly at full power spinning a generator. There have been experimental and even production locomotives employing that system, but even they turned out to be failures because conventional diesel-electric locomotives end up with significantly less buy-in and running costs, with similar efficiency ratings.
Chevrolet had a concept with a turbine-powered semi-truck; the Turbo Titan III
Beautiful vehicle... but just a bad idea.
If she would have had a more reasonable powerplant, that could have been a very progressive truck with improved aerodynamics and dual-width single rear tires; that the heavy truck industry is just now making a switch to.
@PottoGadd I love the first generation Challenger... but I like the 2nd gen as well. Mostly because that's a Mitsubishi Galant from Mitsu's golden years. I feel as though the Challenger nameplate did that car more harm than good. I had a similar issue with the Infiniti G35s here. I used to hate them because they bore the Skyline badge; which frankly it shouldn't carry. It's a great car; likely to be the replacement for my Altima actually... but she's not a Skyline.