Check engine light on No heat dies often but starts back up

Hi, this is Bo, an auto expert on RepairPal's Car Genius team! Your Lincoln LS sounds like it's having a bit of an identity crisis. Welding the catalytic converter on backwards and placing all the sensors after it is like putting the cart before the horse—it's bound to confuse the engine's computer. This could definitely trigger the check engine light and cause performance issues. As for the no-heat situation, if the heater core was flushed but you're still getting cold air, it might be a thermostat issue or a problem with the blend door actuator. The dying at idle could be related to the exhaust setup or possibly a vacuum leak. And that whining sound? It could be a power steering issue, but given the other symptoms, it might be worth checking the serpentine belt and pulleys too. I'd recommend getting the exhaust system sorted out first, as it could be the root of several issues. If you need any further advice or want help finding a trusted RepairPal shop in your area, please feel free to call us at 877-913-1554.