1. A compression test would be a good thing to have, but most dealers will either not do it or do it wrong.
2. Make sure your car has the latest PCM flash and recalls Below are the major recalls that seem to have affected most people. Most are simple and can be done by the dealer in a day.
a) PCM (Powertrain Control Module) Flash The RX8 has a very complex computer driving the engine that has gone through several firmware upgrades. Make sure your on the latest PCM flash from the dealer.
b) In the summer of 2006, a major emissions related recall was conducted on 2004-2006 RX8s related to catalytic converter, and in some cases engine failures. For most people, the recall simply involved a PCM update, some owners had faulty catalytic converters replaced, and some owners had engines replaced. If you own a used vehicle, make sure recall 4206F was performed.
c) Ignition Coils older cars had coils that overheated and would misfire, its easily to tell by flipping a coil over and looking for a burn spot on the back side of the coils. Mazda redesigned the coils in 2006.
d) Starter and Battery the original 04/05 RX8s had a weak starter and battery that could contribute to flooding. Hard starts are the main symptoms, and the dealer can install an upgraded starter battery package to fix the issues.
e) Upgraded Spark plugs along with the starter, the leading spark plugs went through a redesign in the 2005 to help with flooding issues. These improved plugs should be the only leading plugs you buy. (part #NGK RE7C-L)
f) Rough Idle the Engine mounts and mount brackets were redesigned in 2005 to alleviate rough idle issues. Heat from the exhaust manifold can also damage the passenger side engine mount. Check with you dealer about an upgrade if this is an issue.
3. Check to be sure that all the TSB's are done before you buy (if possible) - The are available here.
Clicky
Tell your friend to do A LOT of research BEFORE he makes a purchase. An RX-8 can be a great car, and despite the reputation, it can be reliable and provide many years of fun motoring, but education is the key to making this a reality. Owning and operation an RX-8 is diferent taht most other cars. Maintenance and proper operation can be the diference between happiness and a blown motor.
BTW: lots more info in the link in my sig.
