17 SI 2D Misfiring P0304 P172 and P0219C+F, Emission system, Traction control, hill assist, etc. problems, any help is appreciated

TheKingCoil

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It's been a journey with this car. Bought it brand new in 2017 w/ 50 miles on it. No real issues until about 6 months ago. 35,900 miles as of today. Stock everything except battery.

Issues started a while back, first thing to pop up was "Emission Systems Problem" and only that. Looked it up at the time and most people agreed if it’s just that and no other issues, probably just a sensitive knock sensor. It went away. Then came back and kept flipping back and forth until about a month ago where it has stayed on permanently. Car didn't feel any different, so I went the dumb route and tried ignoring. about 5 other electrical related systems started giving me warnings about them not working on top of the emission system one, things like traction control and brake assist and such.

Then the real problem happened, my car misfired, flashing CEL and all. Immediately took it home and parked where it has been since. It was time to get to work. My bro-in-law is a budding mechanic and has most of the tools needs, so first we checked codes. It was throwing P0172 (System too rich bank 1) P0219(both E and F) and P0304 (cylinder 4 misfire).

We hit the list, checking spark plugs first. They were absolutely burnt to a crisp, like no joke they were matte black. Was like oh here's the problem, replaced them with new NGK ones easy peasy. Same issue and codes persisted. Okay so let’s check the Ignition coils next. We did the listening test, heard the clicking, but to be sure we swapped the coils of 1 and 2 with 3 and 4, and still the cylinder 4 misfire, so it’s not the coils.

Next thinking it might be a faulty sensor, I said fuck it while we are at it let me just change the two in the engine bay. I have a friend who works for a Honda dealership, so he gets me discount on parts, picked up both sensors and slapped them bad boys on there. Took out the MAF and cleaned it off. Same issues and codes.

My bro-in-law was like ima check the fuses next. TBH I'm not too sure about how that part went cause I was at work, but when I got home he said all fuses seemed to be functioning and charging normally. I read that these cars came with pretty terrible stock batteries, but I had already swapped it for a Duralast Gold M51 so it's not that either.

After hitting the forums, I saw that allot of SI’s are having injector problems, so we then spent two days taking those out, testing them and cleaning them. They were pretty clogged and dirty, but after our hard work now each spray a fine mist and look nice and shiny, but to no avail. After putting all 4 back in and all back together, the car ran pretty great for maybe 10-15 miles then boom all the lights and a flashing CEL.

The next things we are going to change (unless one of you amazing people have a better lead) are the knock sensor and maybe speed sensor, and then maybe run a compression test with another friend’s tester.

If anyone has any tips and leads or advice or anything, please drop them below, and hopefully we can help future people with this same problem.

Extra: Because of the blackened plugs, I was like oh man I hope the rest of the internals don't look like that, so I went and got some Seafoam and tried using it through the intake, but for some reason like little to no smoke came out of the exhaust, does anyone know why this is and think this is weird too?
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TheKingCoil

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The filter does need to be changed, could something as simple as that cause such extreme reactions? MAF was cleaned, is there a way to test its functionality?
 

Chilly613

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The filter does need to be changed, could something as simple as that cause such extreme reactions? MAF was cleaned, is there a way to test its functionality?
Yes, sometimes it can be something that simple. Especially if your filter is clogged up. Your car will compensate with extra fuel for the lack of air to make up the loss in power, causing you to run rich. That's why your spark plugs are covered in soot.

Replace your air filter, clean the MAF again just in case, and clear your codes. Monitor your AFR, if you're still throwing a code and running rich, the MAF might need to be replaced.
 
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cota

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The filter does need to be changed, could something as simple as that cause such extreme reactions? MAF was cleaned, is there a way to test its functionality?
if it is stock, it should be able to run as expected if you unplug the maf. I'm not too sure though
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