* Your Owner's Manual: Check the owner's manual. While not all have detailed vacuum diagrams, some do include simplified schematics.
* Haynes Repair Manual or Chilton Repair Manual: These are readily available at auto parts stores and online. They usually have detailed vacuum diagrams specific to your year, make, and model. This is likely your best bet.
* Online Forums (e.g., ChevyTalk, ThirdGen.org): Search forums dedicated to Chevrolet vehicles. Specify your exact model (e.g., "1991 Chevy Caprice 305 vacuum diagram") for better results. Members often post diagrams or links to them.
* Auto Parts Store Websites (e.g., Advance Auto Parts, AutoZone): Some auto parts store websites offer online repair manuals (sometimes for a fee) that might contain vacuum diagrams.
* A Local Mechanic: A trusted mechanic might have access to service manuals with the diagram or be able to draw one based on their experience.
Important Considerations:
* Specificity is Key: The more precise you are with your vehicle information (year, make, model, engine specifics – TBI, TPI, etc.), the better your chances of finding the correct diagram.
* Diagram Variations: Remember that small variations in the vacuum routing can exist based on options like air conditioning, cruise control, and other accessories.
If you can provide the specific model of your 1991 Chevy (e.g., Caprice, Silverado, Camaro, etc.), it would greatly improve the chances of finding a relevant vacuum diagram.
