I had multiple miss fires in the past, changed 2 coils, & plugs. Problem went away then 3 months later it came back started having multiple miss fires again so, I changed the plugs again & reset the codes after idle was smooth again, went for a 40 mile ride & on the way back home the miss firing got so bad at idle & acceleration, I thought it was going to stall at the stop lights. Checked plugs & they’re good coil packs still are in excellent condition, all vacuum is good. I don’t know where to go from here?

 

I am going through this my self with my daughters 04 TL. I have misfires on all, i think i narrowed it down to one coil.
Have you tried pulling the coil one by one when the car is on at a time to see if there is change in idle?
From what I have read one bad coil can cause multiple if not all cylinders to misfire.
I also read that if one or more coils go bad you should just change them all, how many miles do you have the the car?
Question for you, when you replaced your coils where the coils all the same? When i look on Rock Auto to buy all six coils they just have one kind/model.

 

Thanks for your reply, put me at ease for the day. I read it could be a sign of “internal failure” & of course I thought the worse. I heard it could be battery &/or alternator because the system works at a specific voltage & not under but, I think it might be more coils? Like you said. It did start with #4 coil going bad but, I replaced it & it ran good all summer until now that it got cold. I’m going to try your suggestion & get 1more coil & move it around. The plugs still look good. I’ll let you know what I find out.