MisFire and Flashing EML.. Help?

Chris1612

Hi all.
About 2days ago my Astra Coupe developed a misfire in Cylinder 4. It was sudden with no big noise to indicate anything had broken. Also found that the back box has a crack in it. Could this cause a misfire? Me and my Mechanic freind cleaned all the spark plugs as could have been dirty No.4 was manky. All cleaned but no change. Im hoping that it could be happening because of the back box, with the EML flashing, which according to the handbook means a fault has occured which could cause damage to the Catalytic Converter. Its getting a compression test done today and going to put it under the Diagnostic see if we can get a Fault Code
.
So is it possible that not enough back pressure could be causing the misfire? Or is it pure coincidence that the back box went at the same time as the misfire started?

Any got any idea?

Cheers

MikeS

if compression and spark & fuel is oki then check your pre cat / cat for blockage

as the misfire is showing on a specific cylinder then it could well be compression, spark or fuel

Chris1612

Doing a Compression test today, Plugs were fine Oil is fine. I thought my PreCat had 'fell out' a while and did plan to take it out but the rattle went way so I forgot about it. Al get the exhaust off today and look

vocky

also worth checking the injectors, they have been known to fail, swap them around and see if the fault moves