2004 Mazda Rx-8

The 1.3L Renesis rotary engine is extremely susceptible to flooding when the engine is started and shut off before reaching full operating temperature. Unburned fuel washes the oil seals and collects in the combustion chambers, making restart impossible. This is the most commonly reported RX-8 issue and can happen after moving the car a short distance in a driveway or parking lot.

Never shut off the engine before it reaches full operating temperature (the needle must be in the middle of the gauge). If the engine floods, remove the spark plugs, crank the engine to clear fuel from the chambers, reinstall plugs, and attempt restart. Holding the accelerator to the floor while cranking activates a deflooding mode. Maintain strong ignition by replacing spark plugs every 15,000 miles and coils as needed.

The apex seals in the rotary engine are the equivalent of piston rings in a conventional engine and wear over time, causing low compression, hard starting, reduced power, and excessive oil consumption. Once compression drops below approximately 6.5 kg/cm2 on any rotor face, the engine will run poorly or fail to start. This is considered the rotary engine's natural wear item.

Perform a compression test (rotary-specific warm compression test) to determine engine health. If compression is low, the engine requires a complete rebuild with new apex seals, side seals, corner seals, and rotor housings if scoring is present. Rebuilt engines are available from rotary specialists. Premix 2-stroke oil with fuel (1 oz per gallon) to extend seal life.

The RX-8's catalytic converter fails at a high rate due to the rotary engine's naturally high oil consumption and tendency to burn incompletely, sending unburned hydrocarbons and oil through the exhaust. The converter overheats and eventually melts internally, causing a severe restriction that further reduces the engine's already limited power output.

Replace the catalytic converter with an OEM or CARB-compliant unit. Address underlying causes: ensure the engine has good compression, replace spark plugs and coils to ensure complete combustion, and check the ignition system. Pre-cats (manifold catalysts) and the main catalytic converter should both be inspected. Some states allow high-flow catalytic converters.

The RX-8 uses a heavy-duty starter motor because the rotary engine requires higher cranking speeds and longer cranking times to start compared to piston engines, especially when warm. The starter motor wears out significantly faster than in conventional vehicles, sometimes failing in as little as 30,000-50,000 miles. Symptoms include slow cranking and a clicking sound without starting.

Replace the starter motor with an OEM Mazda unit or a high-quality remanufactured starter rated for the RX-8's higher current demands. The starter is located at the rear of the engine and requires removal of the intake manifold on some models. Keep the battery fully charged and in good condition to reduce starter load.

The rotary engine uses an oil metering pump (OMP) that injects small amounts of engine oil directly into the combustion chambers to lubricate the apex seals and rotor housings. If this pump fails or its lines become clogged, the engine loses internal lubrication, leading to rapid apex seal wear and catastrophic engine failure. The OMP failure can occur with no warning.

Inspect the OMP lines for cracks and blockage during regular maintenance. Some owners supplement the OMP by premixing 2-stroke oil with fuel at a ratio of approximately 1 ounce per gallon for additional lubrication insurance. If the OMP fails, replace it immediately and inspect the engine compression to assess whether damage has occurred. Monitor oil level closely as the engine consumes oil by design.