Lean on cylinder 4? Logs/plug pics etc.

[Toni]

Well I noticed something interesting today. I was logging when starting up and noticed that it started off with the front and rear different. Then when the o2s starting cycling they came together. Is is possible that something is up when in open loop? Can I force open loop in other ways than cold startup and WOT?

[Toni]

So I tried swapping ECUs same issue still. I did manage to get some more logs together to see maybe what is going on here.


Here is a 3rd gear wot log



Here is a cruise, the guide lines represent the smoothed average. So yea, the rear (pink) is leaner.



Here is a wot with boost and fuel pressure in focus. The scales aren't quite the same but there is something interesting. Boost goes up .81 PSI but fuel pressure actually went down .7psi, so fuel pressure is off by 1.5psi. Not sure if that is anything significant. I would imagine this isn't exactly a big deal as both the front and rear would experience this?





This is a log of after I fixed my aem afpr last summer. I had a similar issue where the rear was running real lean and as it turned out the afpr was leaking because of a worn ball seat and dropping fuel pressure to the rear. You can see how nice this log is (except for the tune of course)

[Toni]

Did a leakdown test as well. I noticed a trend that the front have more leakage than the rear.

1:89
2:96
3:91
4:95
5:93
6:96

Could this difference be causing my issues?

[Toni]

Well, I think it's fixed! I only did one run because it's getting late and I don't like to do testing at night in case something breaks. After doing the leakdown I had everything apart so I decided to try and swap the front and rear injectors. Well I also tried to bend the injector pins to make a "sure" connection to the connectors. Well I did a run and booyah, front and rear now match up. Going to try a few runs tomorrow as well. I REALLY hope this is not a fluke I will be so pissed lol.

[DocWalt]

I wonder why the connectors would wear out like that... I hope it's fixed

[Toni]

I wonder why the connectors would wear out like that... I hope it's fixed

Assuming this really was the problem...
It's weird because they are brand new (<5k miles) injectors and I replaced the connectors with the MSDs about 15k miles ago. Maybe the injector pins are a hair thinner and the connectors are a hair looser?

[Toni]

Well I did a bunch of pulls on the way to work this morning. Looks like everything except the rich tune (to compensate) is good! AFRs match right up! So much fun to drive!

[DocWalt]

Sweet. What an odd problem... Now you just gotta tweak the tune back a bit

[Toni]

Sweet. What an odd problem... Now you just gotta tweak the tune back a bit

Yup! Also, looks like I have to adjust my ebc, it seems to be rising a bit.