Worth replacing all iginition coils when I replace one?

I didn't pay anywhere near that and yes I replaced them as a set I did not use the cheapest on the planet but I did not use denseo replacements I almost never have in any coil over plug application had to use the dense replacements. I've had no trouble with the cheaper aftermarkets they seem to work fine I'll put 50 $60,000 on the latest set of in a 2013. And once you're used to changing them it's really not that bad you can change you can get the tray out and 36 minutes with the wiper assembly and then you're just dealing with four 10 mm bolts and a couple of plugs and the coil over plug extensions are out.

 

The wipers and cowl are just plain in the way ... so "take out wipers and cowl" is a starting step in so many different repair procedures, it's like "chop ½ onion" in recipes. Eventually you can kind of do it with your eyes closed. (Unlike the onions, it doesn't usually make me cry. It's just tedious.)

I guess what I'm saying is I wouldn't use that by itself as a reason to spend extra money replacing stuff that ain't broke. You'll be taking the wipers and cowl out again for something else sooner or later anyway.

 

In general electrical parts are more reliable than mechanical parts... Your car had one tiny moment of weakness and throwing money at it without being patient and waiting for more symptoms is most likely a waste of money. First step is to change the position of the coils and see if the misfire moves to another cylinder. Of course it's probably not worth until you get another misfire code. Or maybe this isn't a misfire code and you're assuming that's the problem even though it's perfectly normal for an Atkinson engine to run a little rough on start up if it hasn't been running in a while.

 

Nope... First you have to determine the source of the misfire. If it's the coil, then when you swap the coil with the one next to it the location of the misfire will change. If it doesn't then it's not the coils, but something else. But before you even get to this point you have to have the misfire happen again to justify the time and effort involved in moving the coils to different locations.

 

@PriusCamper beat me to it, but anyways:

try swapping the coils around, and see if the misfire code goes with the coil.

If it doesn't, and considering the car has 180k miles, and no mention of previous EGR cleaning, the coils are likely fine, but you might be experiencing head gasket failure.

 

You're likely on the cusp of head gasket failure, due to long-neglected EGR clogging, and that's what the misfire is due to.

Again, I would first swap the coils around, see if the misfire follows.

If it doesn't (and I suspect it won't), that rules out a bad coil, and then I'd do a boroscope inspection of the cylinders, with the coolant system pressurized, look for coolant teardrops getting by the head gasket. Pay special attention to cylinders one and two, which tend to be most problematic.

Alternately, a leak-down test will also determine head gasket integrity.

Basically what's likely happening is coolant is leaking into a cylinder, getting past the head gasket, overnight. When you start up in the morning, the (uncompressible) coolant gives the piston fits as it comes up in the cylinder. Leave it long enough, you can bend a piston arm, punch a hole in the block wall.

And get on the EGR cleaning ASAP. See first couple of links in my signature.

Or just trade it; it's likely to be a money pit soon.