Maintenance:Engine/Decarbonising

Over time, carbon from running an overly-rich fuel mixture can accumulate in your head. This problem is more likely in older, carburettor-equipped engines.

Signs you need to decarbonate your engine

• Engine keeps running on after you turn it off.
• Popping, surging, spark breaking down

How to decarbonise your engine

The easy way

Give it a good thrash for a few minutes. Often a carbed engine leans out (towards stoich) at higher rpm, and the good burn takes some of

With the engine running and air filter off, spray some misted water, or carby cleaner, into your carburettor. Be careful not to let your engine stall during this process. Hold the throttle wheel open a little bit. If you have excess spray around the carburettor, put your fingers over the opening to seal it off and create greater suction inside the carb, and give the engine a good hard rev for a few seconds.

The hard way

Take your head apart, and clean it.

Until someone writes a guide specific to a Corolla engine, refer to http://www.elsham.pwp.blueyonder.co.uk/cx500/decoke/. This page refers to a motorbike engine, but the theory should be the same.