Order from left to right are cyl 1-8. Thoughts on #2? The other side of it is white (clean) like the rest of them. Injectors have had sea foam go thru them and fuel has been Chevron exclusively. These plugs have approx 8k on them and there was a mis-fire under load that has gone away with the Autolites that went back in (unknown mileage on them).







IIRC the original set that came out also had that same cylinder looking a bit odd. Thinking I will grab a coil or two out of JY engine and swap one in since they are cheap and easy to swap. When I pull the plug the next time I will do a compression check. If its a failing injector then will swap all of them over to the Standard Products FJ475 4 hole ones ($28 ea @ rockauto).


Edit: Forgot to add... the Autolites that went back in, measured the plug resistence and found most to be in the 4.7~4.8k range with a couple over 5k & 1 up over 6k. They are spec'd at 4k, I would expect the tolerence to be 20% max so those that were 5k+ are out of spec. Will they work? yes, will work without issue however the amount of energy discharged would be slightly less then the others that are in spec. This is going to be one of those things that you would never be able to detect in engine performance.

 

Those kinda look like they are running lean...... #2 may be pulling some oil due to valve seals......

 

LTFT indicates that as well (lean). I am not finding any vacuum leaks though and the O2 sensor is new. It does still have the evap leak code which is not supposed to be a vacuum leak on the engine. Wondering if that info is false.

 

I think evap only plays a role when the purge valve is open. Which ain't real often, so, likely not the source of the issue. Is LTFT adding fuel? Or pulling it? How old are the O2 sensors?

 

Shoulda tried swapping #2 to another cylinder and seeing if the misfire followed, before pulling them all. That would point to the plug being the fault. If the misfire persisted in cylinder 2, then you start looking at the components for that cylinder, such as coil packs. Did you check the gaps?

 

If I remember it correctly, the + LTFT numbers are indicating that it is pulling fuel, - LTFT numbers are adding. I see + numbers ranging from ~1 to 10 while driving. This is the first time I have been monitoring LTFT & STFT numbers so I have nothing to compare against.

O2 sensor has 4~6k on it.

Have not checked the gaps on the outgoing plugs yet, plan to measure resistance and inspect them (and measure the gaps). I did gap them (0.040") before putting them in, always do. On the old ones I re-installed, I opened up the gap, took a file to the ground and cleaned it up real good to see where the future arc begins to hit (removed the arc pits). Looked at the plug tips with a loupe I have to get a good visual. Once they were cleaned up, I re-gapped all of them to 0.040".

Edit: @Dodgevity Yeah forgot to add that the coil move whould be the first and easiest change.

 

+ is adding fuel, - is removing fuel. (relative to the tables it runs by.) O2 sensor clues the PCM in as to which way it needs to go thru some magic of STFT, and time. The range you are seeing is considered 'normal'. There is always going to be SOME variation.

 

truck again gave a 17.05x mpg tanks with the old plugs in there, it is consistent with the 17~17.1 range. I think the last tank with the old plugs was mid 16's though, but it did have a mis-fire under heavier load.