2009 Honda Fit manual has a misfire on cylinder 4.about 2 months ago hail I was on the highway the check engine light started flashing for cylinder 4 missfire I had my scanner on me and I reset the codes on the nearest exit and everything seemed to be fine for about a day or so then the cel came back on and even after resetting the code as soon as I hit the eceloratore peddle it would persist. I have replaced all injectors all coil pack and all spark plugs. (I also swiped out injectors and coils to see if it would switch cylinders and it has not.
I replaced the motor 5 months before this happed and it ran mostly fine (it seemed to have a little studded in the engine when excelling out of Low rpm but no cel or anything alarming). I tracked the issue down to cylinder 4 injector wasn't getting pulse after hitting the execrator peddle . I really am kinda lost with this and I would consider myself being pretty car savy. if anyone could help me out with this it would be much appreciated. Thank you.

 

If you have narrowed it down to the injector you can test it to verify.

With the injectors unplugged you should have around 10.3ohms of resistance on the injectors themselves. If your injectors read out of this margin by more than .2-.3 you have a bad injector. The bad news is if your injector is bad so is your ecu, the good news is its repairable. Every injector you swapped into that circuit will also likely be bad or will fail soon and fry the ecu power mosfets.

The injector clips should read 7.3v with key on engine off. More or less means the ecu is bad and the Mosfets need to be replaced the Mosfets themselves are cheap SSD103 is the number of them.

If the ecu is found to be faulty, you can repair it or replace it. Replacing will mean you need to have the key re-programmed at the dealership, also if the ecu is found to be bad I suggest replacing all your injectors along with the ecu replacment or repair. I made the mistake of only replacing one but another that I swapped out to test failed a few weeks later and my ecu had to be repaired a second time.

lastly if you figure it out please let us know what you find, it’s very helpful to others in the future :-)

here is a link where I discussed it further.

https://www.fitfreak.net/forums/2nd-...ml#post1463531

here is a video of the repair that was done to my original ECU when my injector failed. Please note the mosfets are not hard to replace for a good repair shop like the one I used below, getting the ecu open takes a lot of time a patience with a heat gun and some prybars.

https://youtu.be/EGg6KeNwjlU