Chrysler was the first American automaker to create a system that tried to improve emissions by doing more than just utilizing a catalytic converter. At the time, catalytic converters led to large power loss and were not reliable, which led to higher maintenance costs. The goal of Lean Burn was to improve on emissions without utilizing a catalytic converter, which might lead to better reliability and performance, as well as buyer confidence when introducing new emissions devices to comply with regulations. However, Chrysler decided to try a different approach, by using fairly new technology, like circuit boards and computers, which were rarely found in vehicles from the 1970s. Chrysler had a lot of experience with cutting edge electronics when working with
NASA in the 1960's and 70's, as they helped pioneer many things, like designing the first stage of the Saturn 1B rocket that was used in the early Apollo missions, such as the moon landing of 1969. This resulted in other firsts too, like creating diagnostic trouble codes for their cars in the 1980s, which was similar to the extremely complicated electronics systems that were used in the rockets they helped design. Their first attempt ran from 1976-1978, where they didn't utilize a feedback carburetor at all, but instead had a spark computer on the air cleaner that adjusted the spark advance while the engine was running. When the engine is warmed up, it would advance the timing more and more to work with a very lean running variant of the Carter Thermoquad carburetor, which worked like other carburetors with leaner jets to run at a very lean 18.0:1 AFR. Over time, while the vehicle was driven, the timing would continually advance in steps after the vehicle warms up, and every minute that has passed, up to a certain time, would result in a more advanced timing setup, and every minute that has passed when idling would remove timing, to be as efficient as possible. The issue was it made the car feel "gutless" when trying to accelerate, so later advancements in the system helped to simplify and reduce this feeling. Reliability also suffered due to being placed on the air cleaner, which was the greatest flaw in the system. Later systems improved on this but this design ultimately sealed the fate of this unique system. In 1979, a feedback carburetor (Holley 6145) and oxygen sensor were added to some models with engines like the slant 6, but only for California, but for 1980, it was used on cars in all 50 states. Catalytic converters were added too, to try to meet the ever tightening emissions regulations. This new system utilized a mixture control solenoid to adjust the amount of fuel it would spray in the system, based on the values sent to the computer from the oxygen sensor,
throttle position sensor, and temperature sensor. This very early system worked almost like electronic fuel injection, and was used for designing the electronic fuel injection system in the 1980-81 Chrysler Imperial, which ended up being very unreliable and was discontinued. The system was continued on the 2.2L in the
Chrysler K Car, but was not included on trucks or vans due to the emissions laws being less restrictive. By 1984, the earlier issues in their electronic fuel injection system was fixed and over time, many vehicles swapped over to it, and utilized an onboard diagnostic system pioneered by Chrysler. Other vehicles went on to utilize the GM system with a Rochester QuadraJet E4M, which was a different feedback carburetor with a similar usage of solenoids and oxygen sensors. == General Motors (1981-1990) ==