* Your Corvette's Owner's Manual: The most likely place. Check the section on engine maintenance or electrical systems.
* A Repair Manual: A Haynes or Chilton repair manual for a 1990 Corvette will definitely have this diagram. These are readily available online and at auto parts stores.
* Online Forums: Corvette-specific forums (like CorvetteForum.net) are great resources. Search the forums using keywords like "1990 Corvette spark plug wiring diagram," "1990 C4 spark plug firing order," or "1990 Corvette ignition system." Someone has likely asked the same question before.
* Factory Service Manual: This is the most comprehensive source, but it's also typically the most expensive. You might find a digital version online, but be cautious of copyright issues.
* Auto Parts Store Websites: Some larger auto parts store websites (like Advance Auto Parts, AutoZone, or Napa Auto Parts) let you look up diagrams based on your vehicle's year, make, and model. However, they might not always be detailed enough.
Important Note: The firing order is crucial. Connecting the spark plugs incorrectly can cause serious engine damage. If you are unsure about any part of this process, it is best to consult a qualified mechanic.
