2013 Honda fit trouble starting, rough idle, stall.
 

Hey guys

New poster but I've read these forums a few times before in search of the answers to other problems.

I have a 2013 Honda fit that wash running aok a week ago. I was going on vacation, and parked it at a relatives where it sat, undriven for 7 days. During that time away, there was very heavy rainfall and high, humid temps (31 degrees Celsius.)
When I picked it up, my girlfriend started the car while I went in to say thanks. I came out after a few minutes and hopped in the driver seat and headed home. Drive home was a relatively normal, except I thought I noticed a bit of a shaking when idling and maybe a bit of hesitation when accelerating. Got home, didn't think much of it, shutdown, went inside and left it alone for about 3 hours.
Later, I went to go out, but when I started the car, instead of idling at 1000ish rpm, it would drop right down to 500rpm, maybe less , sometimes even stall out , just sitting in park.
​​​​​​I left it for the night, it was late. I tried looking it up online. Sounded like maybe valve adjustments? Coil pack? Fuel filter seems a push, it's a lifetime item afaik.
Then this morning I go to try again, same thing. Fluctuating rpm. Stalls out on its own, but definitely if I change gear (automatic). Then I try Again. Now it won't start. It trying to turn over, battery sounds strong but no start. Tried again after adding new fuel from Jerry can and a fuel cleaner and it idled at 1000rpm,but was kind of sputtery. As soon as I changed gear, it just died.

Im so shocked by how it just happened while I was away. No one else drove it and it went from perfect to not being able to start sometimes out of nowhere. Would the valves go that fast? Coil packs nuked by humidity or moisture or something? Cracked?

Any insight is great.
Honda dealer can't look at it until Friday.
Thanks!

whats ur mileage?

any codes pop?

Just over 90k.
No CEL. Haven't checked for codes I don't own a reader atm.

Thanks for your help!

All of the retail car part stores around me will bring their code reader out to the car to check. Not sure what you'll see since no CEL.

Guy from work is gonna lend me one just to see if it's spitting anything out.

No codes? No problem. Let's go old school. Cars need 4 things: Air, Fuel, Compression, and Spark to run. So what's missing from your Fit? Let's go from the easiest to hardest, I'm assuming you don't have a ton of tools or time to waste.

Easiest to check is the air cleaner. 7 days unattended in heavy rain might mean a small animal got into the air cleaner looking for a dry place and plugged it while making a nest. Who knows, it's not uncommon. Odds are against this, but it's the cheapest and easiest thing to check.

Next is the battery. You say it 'seems strong', but a check with a multimeter will tell you if it's putting out the right power. Here's a how-to video: Check for corrosion, a decent amount can be enough to negate the flow of electrons and prevent a car from starting. It's also a good sign that the battery may be close to done. If the battery is original, it could be time to replace. Maybe those 7 days of sitting in the heat could boiled off the electrolyte that was left. My useless online guess is it's the battery. Summertime heat kills batteries, and you were lucky that the 5 year old battery got you started, but the alternator couldn't bring it back to life on that last drive, now it won't start.

Next step hardest is spark. You said it was super heavy rainfall, maybe some water got into the spark system? Silicone spray is great a displacing water, and if the battery has been eliminated as a culprit, I'd start spraying some silicone spray between the plugs and coil packs. Then I'd look into the coil packs themselves, check the resistance. Not sure how many miles are on the car, but replacing these packs around 100k isn't uncommon.

Once you're confident it's not the coil packs, next step is to investigate the fuel. I'd check the (in order of easy to hard) relay, pressure, injectors, pump.