Engine Flooding

RX-8 Engine ‘Flooding’ is not strictly a common fault as it can only be caused by user error. That said it does happen regularly and so warrants an article, best suited to, our Common Faults section.

It is important to not mistake ‘flooding’ issues with Hot Start Problems. Hot start issues occur when the engine is warm. Flooding can only occur when the engine is cold.

Basically; if an engine is turned off during its Cold Start Cycle, it has the potential to flood.


The Cold Start Cycle is designed to help warm up the catalytic converter quickly to ensure that it is working effectively, as soon as possible. This is important for the environment and global warming; all car manufactures are under a lot of pressure to ensure that there vehicles are as clean-running as possible and so getting the catalytic converter up to a good operating temperature quickly, is very important.

The cold start procedure consists of pouring excessive amounts of fuel into the engine (similar to a choke) and then pumping fresh air direct into exhaust gasses as they enter the exhaust manifold (this is done using a secondary air injection pump which sits on the left hand side of the engine under the bonnet). The pump is basically feeding the fuel additional oxygen to give it another chance to burn, helping it heat up the catalytic converter. If the engine is switched off during this operation the un-burnt fuel is left inside the combustion chambers and thus ‘flood’ the spark plugs.

Essentially the mixture of fuel & air inside the combustion chamber is too rich to burn using the spark plugs alone; the mixture needs to be diluted in order to enable the car to start again. If the engine is continually cranked over, the flooding will only get worse.

[ ! ] BEWARE: Continued attempts at de-flooding will eventually cause significant damage to the engine and the starter motor. So caution is advised.

De-flooding an engine can be an easy and simple task. Or it can be extremely difficult and frustrating. It generally depends on how badly flooded the particular engine is and unfortunately, just attempting to de-flood an engine can easily make it worse if you are not experienced in de-flooding. If you are not confident de-flooding the car at home it is recommend that you contact us for additional advice.We can either have your car brought to us or possible have someone carry out the work at your location if fairly local.