I have a Civic EK3 with a d15z6 engine (EDM) and been trying to figure out why I have such negative fuel trims for months now. Here are my logs (from Hondash):



What was done/replaced:

- All filters
- Fuel injectors
- FPR
- Cleaned TB
- O2 sensor

I'm running out of ideas. Any help?

 

https://gtc.ca/blog/long-term-fuel-t...rim-fuel-trim/

 

I've done my research and checked those possible causes, except the cat. But I assume that would cause other symptoms.

 

I just wanted to confirm, are you throwing a code? Also, you may have to watch videos of how technicians use those data and how those data change over time to properly diagnose problems. I use to watch "Shroedinger's Cat" on YouTube, the free channel, to chase a lean code on my Rav4 because replacing parts was not in my budget at the time. Added with the fact with that particular car, the TCM throws a code in conjunction with any engine code, so cruise control was disabled.

 

No codes. I disconnected 2 hoses, one at a time and watched the fuel trims. When I disconnected the breather coming from the valve cover, the fuel trims didn't change. When I disconnected the PCV hose, the fuel trims went from -18.0 to -16.4, which indicates some blow-by, but not the main cause.