I Bought it in Feb 2020. I have no idea about owners before me or any warranties it may have. Car had p0420 code when I bought it from the car lot. Fast forward 6 months later, around Sept 2020. The car started to skip (misfire). Took it to auto zone, code for cylinder 2 misfire. Parked it for a month. Then, Replaced the spark plugs, coils/boots (all 4). It worked!!! Ran fine until Jan 10, 2021. CEL popped up, P0420 code again! Drove it to catalytic converter shop, they said there is no problem exhaust is fine. I had no symptoms just the light. Put in seafoam, CEL is gone!!! 2 days later for the first time ever, I ran it low on fuel (the light came on.) Since that day (7 days ago) it has RANDOMLY SPUTTERED! It does it the most when at red lights, or going uphill. Does it some when at idle, some days doesn't do it AT ALL!!! WE DID A VALVE ADJUSTMENT YESTERDAY praying it fixed the problem. NOPE! Now I'm at a crossroads, fuel pump (because i ran it low and it possibly sucked up trash.) Or Catalytic converter???? PLEASE HELP! OPEN TO ANY ADVICE! It's a automatic btw!!!

 

Scan it for codes again see which cylinder(s). Most of the time its still a bad coil if its sputtering especially if you replaced them with cheap ones. There are also fake NGK plugs out there so check those if possible (and sometimes plugs can loosen on these engines)

 

I have NO codes now! I have swapped them around to see if codes pop up, and nothing. I Bought hitachi brand coils. They are fine when swapped around, the light random sputtering is still there. I am starting a new job feb 8th and am so worried its gonna break down on me. Idk if I should replace the fuel pump or catalytic converter! Thanks for replying!

 

If you have a scan tool you can watch oxygen sensors and fuel trims and that would help.

Generally a bad cat will cause the car to “bog down” where it won’t let you go into the higher rpms at wide open throttle. I’ve pulled upstream o2 sensors to confirm a restriction before.

Fuel pump issues generally will kill your acceleration in general and with the sock style filters on pumps combined with plastic tanks its pretty rare for a debris issue. You could try spraying a little extra fuel(carb clean works well) into the intake to see if it smooths out while idling.

Have you run enough gas through it to rule out a bad fill up?

Any vacuum leaks?

The reason I suspect ignition is mine would stumble at lights and on light to moderate throttle heading up hills.

Check your coil boots for any weird spots they may be arcing to the block.

 

Make sure it has NGK or Denso Iridium spark plugs.

In general, a GD Fit will run forever as long as it has NGK or Denso Iridium spark plugs, Denso or Hitachi coils, and a current valve adjustment. That usually gets them to over 400k miles.

When our fuel pump failed, at around 180k miles, it just dead stopped pumping. I think your problem is likely spark plug, coil, or valve adjustment related.

 

We sat the valves at 0.06 intake- 0.10 exhaust. It was doing it before and it hasnt changed, still doing it the same. Valves on exhaust were shut completely couldn't even fit a 0.02 in there, it was the smallest one. It sounds alot better at idle and even while driving since valve adjustment. I'm not sure how to check for vacuum leaks, but my car drives fine even at high RMPs only a random sputter. It can actually go a whole day without the sputter, as well. I am driving to Honda dealership today. They said they will run diagnostics on it for free. I hope it's more thorough than the reader autozone has. I am worried to death and dont even wanna drive it! The plugs I bought are Auto lite brand from auto zone. Coils brand new Hitachi brand (all 4). And speaking of the gas, yes I ran it low the day the fuel light came on for the first time EVER. I put only $10 in it, and as soon as I left the gas station it started to skip!!!!😵 I poured the seafoam in with a 1/4 of gas I got (possibly bad) then ran it out. Poured a half a can of seafoam in it then used shell 93 premium to fill up. I AM ABOUT TO PULL MY HAIR OUT WITH THIS CAR!!!!

 

Replace those Auto Lite plugs with factory NGK Iridium's or Denso Iridium. Especially if they sold you platinum plugs. The car is spec'd for and shipped from the factory with Iridium plugs.

 

Shell premium is a great choice for fuel. I'd skip the additives.

 

Yep, and I'd also double check the gaps.

 

What do the gaps need to be?

 

Run's best at around .040". More gap puts more strain on the ignition coils. We are nearing 200k miles on stock coils and I attribute it partially to running Iridium plugs at a small gap. Also worth noting the the spark plug gap opens over time, so I like to start low.

 

I HAVE A NEW SYMPTOM!!! Turned on my car to take it to the dealership, let it get warmed up, and it started Making a puffing sound out the muffler like something is blocking the exhaust air flow. Every sputter makes a "puff" sound. I couldn't drive it there out of fear of breaking down. I also realized we didn't adjust the valves in firing order. I don't know if this may have part in the random skipping, but we will be readjusting them in the firing order today! I am so beyond frustrated!!! I love my fit, but it's starting to get aggravating!!!!😵 If it helps, it gets hot before it randomly skips. Never does it cold.

 

Focus on what I said here...

"In general, a GD Fit will run forever as long as it has NGK or Denso Iridium spark plugs, Denso or Hitachi coils, and a current valve adjustment. That usually gets them to over 400k miles."

Your problem will be solved with one of those 3 things. I would re-do the valve adjustment and install the correct spark plugs.

 

Will do TODAY!!!!

 

Wishing you luck!!!

 

Thank you very much!!! I just got back from Oreillys with NGK spark plugs! The guy there said it couldnt be why it threw the P0420 code months ago but I read online, using the wrong plugs could cause unburned fuel to go through the exhaust and cat. Which could damage in the long run the cat. I hope thede plugs are the cause of ALL MY ISSUES!!!! FINGERS CROSSED & PRAYING HARD!!!🤞🙌

 

NGK Iridium? Short number on box should be 6774. Long number on plug is IZFR6K13. Just want to make sure.

Good luck on the valve adjustment as well. Double check each one with bent feeler gauges to make sure it's in spec.

 

So what was the outcome? Having similar issues and looks like I may need to replace my plugs. I think they are platinum.