My vehicle keeps cutting out

I OWN a Toyota Tazz 130 with about 235,000km on the clock. My problem is that it keeps on cutting out and I am always replacing plugs.

I can't just start and go. The plugs look burnt when I take them out. What causes that? - Phumzile

ADVICE:

Phumzile, if by "burnt" you mean the electrodes are partially melted, it points to overheating, possibly due to pre-ignition or to the plugs being too "warm" for the engine.

Ask at a spares shop what the normal heat range plugs are that Toyota recommends for the Tazz.

If by "burnt" you mean the plug faces are covered with shiny soot or carbon residues, too much oil is getting into the combustion chamber.

This can be caused by hardened valve stem seals, a blocked engine breather or worn oil control rings, the latter case meaning an engine overhaul is on the cards.

If the plug faces are covered with velvet-like, dull black soot deposits, the fuel mixture is too rich or the plugs are too "cold" to burn off the deposits formed during short-distance driving.

It's also possible that someone has fitted overly warm plugs in an attempt to prevent oil-fouling.

Are you sure the problem is not in the plug leads, rather than in the plugs? Dodgy plug leads will cause misfiring, which will result in carbon deposits on the plugs.