2018 Civic Sport help.....catalytic converter?
 

I'll start by saying I know I'm going to have to take this into the dealer soon - but just wanted to put my mnd at ease until then. I work a strange schedule and it's hard to get there. It only has 4800 miles on it (rate about 550 a month)

Just about the time the weather started turning here (end of October) my average mileage started dropping. I wrote it off initially because of the cold. It was at 41.3 at it's peak, and is now at 37.1

A couple weeks back, we had some "swings" of temperature, but I never let my tank get below 1/2, so that shouldn't have been a problem.....however, I noticed some "chugging" when decelerating once in a while, so I put some STP in and filled it up. Ran a tank of premium in the next tankful too.

In the last few days, it's started "missing" again when decelerating......and, when I shut it down, many times there is an excessive cloud of white smoke and a smell of gas and sometimes sulphur.

I'm assuming this is likely some kind of converter issue, but wondering if anyone has any ideas or past experience. I'm on my 16th Honda and have never had anything like this before

lets hope is not your cat, that's a 1300.00 est cost, although the dealer will have to make it good if it has failed. sounds like a possible idle cut off may be dirty, when my cat on my fit went bad, it only gave me a engine light, ran good, no misfire. reset and it came back on quick. since you have no engine light, doubt it to be the cat.

Check your oil. White-blue smoke can indicate engine oil being burned, and some newer Hondas have had piston ring issues.

Showing 50% oil life left at 4800 miles and change. I'll "dip" it later on....

Yes - oil level is fine....

I've been wondering if I've been driving this one too "easy" - my commute to work is 6 miles......3 miles at 55/45 and 3 miles at 35. Many mornings I only stop once for lights. The way I drive I rarely see the tach go over 2.5k.

So, on the way home tonight in the 55 section, I let it slow down to 40 or so a few times and then gave it some juice and got it up over 4k for some short pulses. When I shut it down at home, no cloud of smoke.

Maybe I've just been being way too nice??