Originally Posted by Donwkk
Don't assume the computer is smarter than you - it is not - and don't let it confuse you.
The computer has no magic way of knowing which cylinder is misfiring - it looks at various sensors and makes a guess - the first time around it guessed it was #1 and now it is being a little more truthful and admitting it is not sure which one or more are the problem.
You knew enough to try changing a plug and swap coils so you obviously have some experience doing it yourself - let the computer guide you but trust your common sense and go by past experience.
When you removed that one plug what did your eyes tell you - did it look recent and healthy or old and crusty - if the latter you should replace them all with ACDelco 41-103 as a first step. The proper Delco's work - don't accept whatever brand the local auto store is pushing this week - other brands might work as well but why add another unknown.
Recheck the coils - The front and rear coils can be tricky to seat properly - putting them down into the holes less than straight can result in the plug boot spring and plug top not making a good connection.
If problem remains with new plugs and properly seated coils move on to the throttle body - do a search for throttle body cleaning and you will find many threads and how to's on how and why you may need to clean yours.
Take it step by step and you will resolve the issues.
First off Thank You Very Much for your insight!
Plugs were just changed before about a 1000 mile journey a month ago as it was idling a little rough and it cleared it right up. We used the Bosch Platinum plugs as we heard they were the best for that particular vehicle.
I noticed the vehicle low on transmission fluid and added some and it is probably a little above the full line and about that time it started missing. We then cleaned the air temperature sensor on the air cleaner hose which helped tremendously and actually replaced it with a new one and removed the Throttle Body and cleaned it.
We then bought a DTC retriever and it popped up with P0301....next was to pull the number 1 spark plug....which was a little oil fouled on the electrode tip.....and not only replaced it but also swapped the number 1 & 2 colis to see if it was the coil in hopes of P0302 coming up telling us it was the coil.
Then the number P0300 came up and threw us for a loop.......I guess with all that said would over filling the transmission have anything to do with this at all?
Thanks again for your time and knowledge as we do appreciate it along with anyone else that might be able to help us.
Have a Great Weekend!