Hi

I'd really appreciate any help.  My zetec had a bad mis fire when I bought it. It did it using gentle throttle, labouring in 4th the worst. By searching through the usual suspects on here I fixed it by replacing the spark plugs, leads, coil pack.  I also did the air filter and fuel filter.  I silicone sealed the washer jets to stop them leaking too.  All this cured the mis fire when driving but now at idle it has an awful misfire that literally shakes the car around, also when using really gentle throttle the car seems a bit off unless you put your foot down. The fuel economy is only 28mpg too and I drive like a vicar. Can anyone offer any help? 

I'd get a compression test and have a sniff test done for head gasket


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Hi, apologies for my ignorance but what is a sniff test? 

A sniff test uses a glass tube and aspirator bulb that pulls fumes from inside the top of the radiator into the test beaker, passing through a gas-sensitive bromothymol blue chemical. If combustion gas is present in the cooling system, a chemical reaction occurs, turning the fluid from blue to yellow, indicating a combustion leak from a head gasket.

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Thanks for your help. I'll investigate further and follow your advice on the sniff test.