Weaver

I have an 04 mercury grand marquis. It has 191000 miles but was still running good.
because of mileage I desided to install new coil and plugs. I ordered cheap ones, all went well for about a day, then it started missing, but not a steady miss. I read that the connectors will do this, so I replaced several of them because they were not fastened. I also called the seller and he has sent me a new set.
My first question, should I bother to install them, second should I also replace plugs? would it be best to order a more expensive $$$ set.

All suggestions will be considered. jweaver252

as I have not heard back about my problem, I intend to replace all the coil. (they sent me more). I know that there still cheap coils but maybe will work this time. I will not replace the plugs because I feel most plugs do their job. I will let you know my results.
As I explained I had no problem until I decided to replace plugs and coils because of high mileage. jweaver252

What plugs did you put in? If you put any of the split fire or E3 garbage they are your problem.

Thanks for you input Stealthee,
I had put in motorcraft.
I have now resolved the problem, for your info. I used the replacement coils for one bank and checked all my connectors.(taping some) This seemed to do the job, its running well ,no miss. For a while there I was worried, old car, high mileage.
Again, i appreciate your feed. I'm not a mechanic but if you ever need another idea or two,please let me know.
jweaver252