Cannot fix Single cylinder misfire under load.

JoshuaK wrote:

I think your #3 injector is firing but allowing insufficient fuel through under load (high cylinder pressure). This would account for the lower positive fuel trims you're seeing because some of the oxygen is being consumed in combustion, but not all of it.
 

It seems as though you were correct! I just got back from a test drive after swapping the direct injectors between cylinders 3 and 1 and the problem moved to cylinder 1! I’m super stoked to have found an issue! I just need to get a replacement injector and do the job again and hopefully she’ll be good to go for another hundred or two thousand!

I really appreciate you guys continuing to work with me through this. I know it’s tough to try to help someone through the internet! 

Like I said before, I do feel a bit stupid for not trying this earlier, but I’m relieved. The direct injectors are under the intake and I just installed these when I put the engine back in back in March! Granted they were rebuilt instead of new, but I just assumed that couldn’t be the issue! Well, I was wrong! 

Thanks again guys! 

I will report back again when I get another injector installed just to be sure, but I’ll go ahead and mark this one as SOLVED! 

Well done!   Those are some excellent captures of the secondary. What probe did you use?

FWIW, this one was the smoking gun for me:

 

The 'tail' at the end of the burn line, nearly as tall as the firing line.

Would love to see some captures with the new injector if you have the time afterwards.

Tyler wrote:

Well done! 

 Those are some excellent captures of the secondary. What probe did you use?

FWIW, this one was the smoking gun for me:

 

The 'tail' at the end of the burn line, nearly as tall as the firing line.

Would love to see some captures with the new injector if you have the time afterwards.

Thanks! I am definitely relieved! I used the picoscope 2204a along with the hantek ht25 and an extension wire. It doesn’t take too long to get the those installed, so I’ll make a new capture when I get the new injector! 

Good work! I'm curious -- How did you hook up the HT25 to your COP?

JoshuaK wrote:

Good work! I'm curious -- How did you hook up the HT25 to your COP?

I got one of those extension high tension leads and used it in between the coil and the plug. I zip tied everything in place so I could drive it like that. 

COP Extension Cord with Earth Cord for Diagnostic Coil-on-Plug Lead (HT308) a.co/d/8wH2kPD