A misfire can have several causes. Bad plugs, wires, coil packs or cap and rotor if fitted to this model. Also bad fuel, vacuum leaks or valve damage can cause this. Wonky injector or CTS Sensor may also be suspect. You need a serious diagnostic from a qualified shop to run this down. Well worth the money in my opinion or chase your tail with the freebie glance from those Irish fellas.

if you don't know the answer to this question do it. fuel filter changed?

sounds like you bought gas with water in it they put anti knock additives it sounds as if your fuel is not hot enough to make it run smooth syphin it out pour it into a clear container let it sit 20 min you'll see two seperate liquids the gas floats pour it off its a ez free test but if it change suddenly that what i check

When's the last time you changed the spark plugs?

I drive a 2002 Chevy blazer. It has been running smoothly but 2 days ago I started it and the engine wa shaking very badly and it felt like my transmission was catching. So we took it to o'reillys and they said that the engine diagnostics test said my engine was misfiring and I needed some part that could be causing that. I don't remember the name but it is circular an goes between the air filter and engine. They also said my transmission was slipping but it was probably caused by low transmission fluid. So I bought the part and fluid and it is running a little better but not good. The engine still shakes a little and whenever I give it gas my oil gauge rises which it had neve done. Also if you don't give enough gas my vehicle jerks and then dies. Any ideas on what it could be!?