It should be in your Owner's Manual. I think it is on page 99 or 100. If you do not have the manual, you will need to either find an image of one online, purchase one online or find someone who has one that they can show to you, either online or offline. If you are still stuck with this, try the Cadillac Owner's Forum, there are many forum members there who own such cars (like me) that would be more than happy to host photos of the diagram for you.
Try e bay.
HAYNES REPAIR MANUAL
See if your public library has a Chilton's book for your Cadillac.
Hi, I have an 1988 Coupe Deville with same issue. Did you ever find out how?
The PCV valve is located in the rocker cover on the passenger side of the engine.
1800oldjunk
http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c15280090549
your local librarie should have a mechanics manuual that you can photo copy ! Good Luck !
go to books4cars.com
What do you want a diagram of?
The best place to find a wiring diagram is in the Cadillac Shop Manual. You can find one on eBay in the $50 range. It gives you the wiring diagram and so much more. Mine is becoming threadbare from use.
To find a diagram for the 1988 Cadillac Eldorado 4.5 liter engine you can consult their main website or contact local dealers.