Service engine light blinks,code read out of po300

If you had swopped 3 to 4 and 4 to 3 components, that would have saved you some money.
What are the fuel trim readings?

Question edited for a lot more clarity.
Question moved to model category.

What did you use to check the code, a simple scan tool, the dash display? A professional grade scan tool computer will tell you exactly which component is causing the number 4 misfire.

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Once you prime it and it starts will it keep running or die again until primed ?

the flashing light is telling you the engine is miss firing, not that there is fuel in the exhust a miss fire is the only thing that will cause the light o flash the P0300 is a random misfire so i cant tell you witch cylinder but replace the coils that should take care of it....good luck

Erase the code and drive it. If it sets a code again or runs poorly, see if any new code(s) are set.

Take it in, a blinking check engine light is not a good sign. Solid yellow is ok, blinking yellow or red is in need of service. Get the codes checked asap.

Well a blinking light is a severe problem and will cause catyaltic converter damage, a bling light is likely a misfire this is the most common reason the engine light blinks because this will cause damage, the first thing you need to do is have the codes scanned, this can be done for free at most auto part stores, they will give you a print out with the code # and discription of the problem , for example the code may be a PO300 misfire. if you get the codes and contact this site again i can help you further, but the next time make sure to list the year, make and model of the car or truck and list the problem again with the code, because if you just list the code it wont make since to someone else. good luck.

a blinking ck engine light means you have a catalyst damaging misfire. the misfire is also the cause of the shaking and probably low power condition. you need to have the vehicle scanned asap and try to figure out which cylinder or cylinders are misfiring by the code read by the scanner. if you have a po300 code it means you have a random cylinder misfire. if you have a po301 through a po306 then go to the cylinder 1-6 designated by the last # in the code to figure the cause from there. look for a burnt plug wire, remove the proper sparkplug and ck it. also remember to change the engine oil as there is unburned fuel getting into it every minute this condition exists that the engine is running. good luck to you.

the only thing i could think of is a fuel shut off switch malfunction

The light is flashing because the engine is miss firing. The first thing I would try is replacing the distributor cap and rotor.