misfire and water useage

[scottambrose]

my s40 2.0t seems to one minute have water at the min level then its at the max. and every now and then it misfires seems worse in the morning, the fault codes are no help just says 3 way cat conv damaging due to misfire.

[daveforber]

Water going up and down may well be normal if it's at minimum on cold and maximum when warm, as water expands with the heat.

If you're continually topping up, then there's a problem either with coolant leakage (from radiator, pipes, water pump) or head gasket, but a head gasket failure is usually accompanied by very high running temperatures.

Misfire is an awkward one to diagnose. First port of call is always spark plugs, then leads, then coil packs. If it's difficult to start in the morning accompanied by a fuel smell and blue smoke, then the fuel pressure regulator and/or pump are both common failures.

[smudgethecat]

ive had similiar symptoms, head gasket was on its way out

[scottambrose]

it looks like as the cat has been removed its over fuelling and running rich leaving excess fuel in the engine and making it misfire now and again when its been left for a while. with reference to the water problem im stumped no leaks from hoses etc.and ive checked the head gasket with blue reaction fluid and it stays blue idicating no fumes in the water. so im stumped/