Technical missfire

[jpd123]

car running fine stoped to un load boot .started ok then stated to missfire just got home.i replaced spark plugs and leads still misfires.dom i change coil packs.:bang:

 

[JLenno]

Are you getting any warning light for temperature inside the car? Which would suggest head gasket.

 

[jpd123]

no lights

 

[JLenno]

Check your water level in the Radiator first. Also check that your Rad fan is coming on.

 

[fingers99]

Check your water level in the Radiator first. Also check that your Rad fan is coming on.

And compression test.

If you swap the coils and the misfire follows the coils, the coils will be the issue. But you need to determine which cylinders are misfiring.

An alternative is to use an insulated tool to remove each lead, one at a time. The one(s) that don't affect the running speed of the engine are misfiring.

Logic suggests that a misfire caused by a coil will affect 2 cylinders.

 

[peterainbow]

Logic suggests that a misfire caused by a coil will affect 2 cylinders.

doesn't have to be, i had one go and was only one lead out, i think the insulation had broken down on one socket on the HT side

 

[fingers99]

It's possible, but not common. Mind you. given the usual neglect, anything is possible on a Punto.