* Your Owner's Manual: The most reliable source. Check the engine specifications section.
* A Repair Manual: Chilton, Haynes, and other repair manuals specific to the 1989 Ford Aerostar will definitely include this information, often with a clear diagram.
* Online Automotive Repair Databases: Websites like AllDataDIY or Mitchell1 (subscription required) contain detailed service information, including firing order diagrams.
* Ford's Website (Possibly): While less likely to have a readily available diagram, Ford's website might have some owner resources that could include this information.
* Online Forums: Search forums dedicated to Ford Aerostars or general automotive repair. Someone may have posted a picture or diagram. However, verify the information from multiple sources to be sure it's accurate.
Important Note: The firing order will depend on *which engine* your 1989 Aerostar has (it was available with a few different engines). Make sure you specify the engine size (e.g., 2.3L, 2.8L, 3.0L V6) when searching for the firing order.
