http://z31.com/wiki/doku.php?id=information:look_for
http://z31.com/wiki/doku.php?id=informa ... c_z31_info
1. Repair Manuals
Spend the $15-20 on a Haynes manual. Don't waste your money on the Chiltons. You should be able to pick on up from any auto parts store that carries the Haynes manuals. Pep Boys or AutoZone for example. Also, download the factory service manual and owners manuals from one of several locations. Currently, they are easy to find here:
http://www.xenonz31.com
2. 300ZX Registry
Please take the time to register your 300ZX via the 300ZX registry. Click this link:
http://www.thezregistry.com/cgi-bin/z31owner.pl
Add your information to help improve the system.
3. Timing Belt
Find out when the timing belt was done last. If you can't find out, DO IT IMMEDIATELY! Instructions are in the Haynes manual. You can ignore the steps about taking off the valve covers and loosening the cam rockers. Timing belts are supposed to be done every 5 years or 60,000 miles. If a timing belt snaps on you, you're looking at a new engine. That's a lot more money than a new timing belt job.
4. Tune-up
Chances are, the previous owner is selling a car that hasn't had a tune-up done in a while. Click this link for parts to replace:
http://www.300zxclub.com/showthread.php?t=15518
Instructions for replacement of these items are in the repair manuals.
5. Vacuum leaks
Vacuum leaks are a common source or problems for the Z31. The entire climate control system runs off vacuum. A small leak anywhere will cause the whole system to not work properly and you'll get hot air coming out of the windshield vents when accelerating. Go to the nearest parts store. Open hood. Take the vacuum line off the fuel pressure regulator (it's a short, easy to reach and remove hose). Have the store match up the size. Buy 30 ft of tubing. Depending on how much it is per foot, you might just be better off buying the spool of 50ft. Don't forget to replace the hose when you get back to your car. Then, starting under the hood, replace all the vacuum lines one at a time.
6. Clunking and Vibrations
Common problems on cars this old. Click and read:
http://www.300zxclub.com/showthread.php?t=135957