Same thing here.
Driving home from work last week, suddenly car started shaking, bad!
Got it home and pulled this code:
Searched "Acura TSX cylinder misfire" and this thread pops up.
Pulled the old spark plugs out:
Installed brand new NGK 6994:
Although I was in need of new spark plugs that didn't solve my problem.
In fact, more codes popped up! Along with my initial code of P0302... now I had P0301 and P0303 to deal with.
Went over my work and everything checked out so I knew that the culprit was most likely a bad coil plug.
Most likely coil plug #2 since that's the cylinder that was initially misfiring.
However, why did the other codes pop up after I changed the spark plugs?
Could it be that now the other coil plugs were going bad as well?
I could've started switching coil plugs around to see which one exactly was causing the problem, but I thought to myself that if one coil plug is already bad, then how long before they all go bad?
I wasn't gonna drive around and stall in the middle of nowhere to find out so I ordered 4 brand new Acura coil plugs online.
Parts arrived yesterday.
Out with the old:
Installed 4 new coil plugs and PROBLEM SOLVED!!
Coil plug part #:
All codes are cleared and car is running like a champ again.
Thanks again to this thread which originated in 2011 and to this DIY:
Sure glad I got this mess all sorted out because I just received my DMV renewal the other day and my vehicle is due for a smog.