This paper presents an action-research project aiming at improving the performance of “just-in-time, just-in-sequence” auto parts manufacturing and delivery in three tier-1 suppliers of the Nissan plant in Barcelona. This research was conducted at the Barcelona School of Engineering (ETSEIB) and promoted by the Nissan factory in Barcelona. In this paper, first, the concept of synchronous manufacturing is explored. After several improvement ideas are spotted within the Nissan plant, the paper focuses on the suppliers. An intervention approach is proposed. Suppliers are categorized and selected suppliers are analyzed (by means of three case studies, each one corresponding to a different type of supplier). This research contributes to understanding how synchronous manufacturing and delivery can be extended to suppliers and the existing drawbacks. The critical variables in synchronous manufacturing , delivery and the relations between them are identified in a conceptual model termed the M-S Model. Implications for suppliers are derived, allowing us to improve the performance of the whole synchronous manufacturing system. A piece of software is developed to help companies schedule a smooth flow of components, making synchronous manufacturing easier. Results may help decision makers develop a supply management system, including policies, procedures and the necessary resource deployment.