A new “Traveling Spark Ignition” (TSI) system which, aided by a Lorentz force, propels a large plasma into the chamber of internal combustion engines, has been developed and tested on a single cylinder 4-stroke engine run on natural gas. Engine test scenarios included: conventional spark plugs with high energy CDI (1ms duration) as well as the new TSI electronics, and specially designed TSI spark plugs with TSI electronics. The TSI system was well suited for conditions where there is poor mixing of air and fuel, greatly reducing misfires. The lean limit was improved by between 6 and 23%. Improvements of nitrogen oxide (NO) emissions when the engine was running at the lean operating limit were up to 80%. One of the TSI plugs was successfully run in an engine at 2100rpm for 50 hours.