Hey everyone, I've had my Fit since March. The first road trip I took on it had great gas mileage. I averaged about 40 mpg. A few weeks later it started acting up, it started to misfire and throw codes. I thought I figured out the issue. Which I replaced the coils and spark plugs. Which the check engine light went away. Still getting terrible gas mileage (23 mpg). I decided to check if there was any codes last week, there was the same codes that popped up before the misfire on 3 cylinders. So I checked to see if it was the coils again. They seemed to be good to go. I put in fuel treatment thing it could be a fuel issue. I unplugged the battery to reset the computer and all the codes disappeared. I drove it til the tank was low. I got slightly better gas mileage but still getting around 24-25. Only thing I could think of is possible fuel clogged line, fuel injectors or possibly bad fuel pump. Is there anything else that I could be missing or anything else I should look at?

 

Did you use OEM parts (coils, plugs) from reputable source?
Honda is new BMW now, any non-genuine part (including air filter element and coolant) causes issues!

 

The coils are Hitachi and I used NGK plugs. I test the coils and plugs. They work just fine. It's definitely a fuel issue.

 

My next take will be valve clearance inspection / adjustment
as well as Gas pump unit electrical plug (it tends to burn contacts)

 

Just to reiterate the above...valve adjustment.

 

I'm in the same boat as you (averaging around 22 MPG) but I recently did a valve adjustment and generally that noticeably improves your MPG so I would look into getting that done it you're long overdue. Some easier things to tackle are tire pressure & oil change.