Lean on cylinder 4? Logs/plug pics etc.

[Toni]

So after I fixed my fpr problem things were running great. Then on my last trip I was showing off and man... the car started breaking up pretty bad after 4-5k. Put the logger on it and sure enough, shit ton of knock and the rear seems to be running lean again. However, this time, the fuel pressure stays rock solid.



I pulled the plugs and checked compression. 150,148,155,155,150,152 (1-6). I noticed plug #4 was much whiter and was flaky. I would assume this is the culprit cylinder.

(#3,4,5)



Clogged injector? Something else? Curious if anyone has an idea of how one cylinder going lean would affect the afr after all three mix. Thoughts?

Thanks,
Antoni

[KeithMac]

Missfires will show up as lean on the Wideband due to unburnt oxygen being passed straight through the engine.

One cylinder running lean will scew the whole bank reading..

The plug insulators look far too white for my liking, should be a brown/ tan colour unless youre running alky.

[Toni]

Well, injectors came back clean. None were having any problems. I swapped the plugs front/rear and gapped them lower. No change. Once it cools down I'm going to swap my windebands front/rear and see if there is any difference.

Missfires will show up as lean on the Wideband due to unburnt oxygen being passed straight through the engine.

One cylinder running lean will scew the whole bank reading..

The plug insulators look far too white for my liking, should be a brown/ tan colour unless youre running alky.

What type of problems would create the white insulators?

[DocWalt]

Have you swapped injectors around?

[Toni]

Have you swapped injectors around?

I did, I swapped them for good measure even though they all flow tested fine.

[DocWalt]

Have you checked the resistor pack? Made sure the connections to the injectors (electrical) were clean and secure? Have you swapped the front/rear widebands yet?

[Toni]

Have you checked the resistor pack? Made sure the connections to the injectors (electrical) were clean and secure? Have you swapped the front/rear widebands yet?

Well I swapped front/rear widebands today and the readings are correct. It is not a bad sensor. The rear bank is still running lean. I tried low boost and it still does the same thing. Will look into the resistor pack next.

[vr4tune]

Have you done a compression test or cylinder leak down?

[Toni]

Have you done a compression test or cylinder leak down?

See initial post...

So after I fixed my fpr problem things were running great. Then on my last trip I was showing off and man... the car started breaking up pretty bad after 4-5k. Put the logger on it and sure enough, shit ton of knock and the rear seems to be running lean again. However, this time, the fuel pressure stays rock solid.


I pulled the plugs and checked compression. 150,148,155,155,150,152 (1-6). I noticed plug #4 was much whiter and was flaky. I would assume this is the culprit cylinder.

(#3,4,5)


Clogged injector? Something else? Curious if anyone has an idea of how one cylinder going lean would affect the afr after all three mix. Thoughts?

Thanks,
Antoni

[DocWalt]

Good to see it's not the widebands. Sort of not good at the same time lol