2017 Honda Accord 2.4 GDI Misfires

Need some direction on this one. 2017 Honda Accord 2.4l GDI non turbo. During full throttle runs, it will misfire on all cylinders (can see on misfire counter), CEL will start flashing and then go into limp mode. Only codes that set are p0300-p0304. Clear them and will run fine again until hard acceleration. I had seen similar symptoms before on the 1.5l Honda engine and injectors fixed the issue. It was decided to try cheap ebay injectors on this one with no change (parts guy at Honda claimed that injectors on the 2.4l engines were uncommon so we didn't want to spend the $600 on a hunch). New aftermarket MAF sensor was installed with no change. Also did a cylinder AF ratio test through the scan tool and all cylinders failed and showed rich. Fuel pressure goes up to 2500 psi during WOT and also there was no drop in pressure when turning off engine, pressure increased slowly. Having a hard time interpreting the data as I am unfamiliar with wideband af sensors. I will post some data captures during or right before the issue occurs and also at idle. Would appreciate if someone could look them over and see if something stands out. Also any suggestions at what other data I should be looking at or any other tests i can do would be great.

Happy to look over your captures.

Also did a cylinder AF ratio test through the scan tool and all cylinders failed and showed rich.

Was a cylinder A/F test done prior to injector replacement? What were the results?

Having a hard time interpreting the data as I am unfamiliar with wideband af sensors

Widebands can be fun if you're unfamiliar. :silly: If it helps at all, the next time you go for a WOT run, you can try the Equivalence Ratio (Actual and Desired) PIDs in Global OBD. They give you a normalized A/F reading, and what the PCM is looking for. 1.0 is stoichiometric. Less than 1.0 is rich, more than 1.0 is lean.

First 2 are during acceleration and last 3 at idle. Also, I believe the original injectors passed the cylinder AF test. I do have in the back of my mind that these injectors are very poor quality and I might have introduced a second problem or just replaced bad injectors with more bad ones. I just wish I could prove the bad injectors. Would a scope be useful in this situation?

Thank you for the screenshots. I grabbed this one for reference:



Was this taken at wide open throttle? If so, I'm a bit surprised by the Air Fuel Ratio only being 14.0. Most makes command a lower AFR during heavy acceleration. Some don't. :silly: There's no desired AFR or desired Equivalence Ratio in the shot, so we don't really know what the ECM is looking for.

On the other hand, the downstream sensor agrees that the mixture is rich. That's a decent indication that the engine is getting enough fuel.

Would a scope be useful in this situation?

Possibly. A secondary ignition pickup on one of the ignition coils during a test drive (while it's missing) would tell you if the cylinder is running lean or rich. As an example, this is a capture I took from a Ford with a failed injector. It's multi-strike, hence the two firing events:



The peaks at the end of both spark lines show the cylinder to be running lean and misfiring. An injector with a poor spray pattern and/or atomization will look similar.

Yes it was WOT.