Plugs dirty after 800 miles

[bdbull]

2010 Avalanche - Had a rough idle problem that was solved with new plugs a while ago, but now I feel like it's coming back after only 800 miles. Pulled a few plugs (1, 2, 3, 7) today to check them out. I could be wrong, but I don't think they're supposed to look like this after 800 miles. They all had oil in the threads and carbon/soot down near the tips. I've already done the oil pan deflector thing and have a catch can on order. I'm thinking I probably need to change out the valve cover also as I've never done that so I assume it's the old design. What else do I need to look at? Is this something other than oil causing this?

 

[Foggy]

What brand and type of plug are you using ???? May just be the wrong plugs
or even counterfeit parts that you installed.

 

[bdbull]

What brand and type of plug are you using ???? May just be the wrong plugs
or even counterfeit parts that you installed.

These are AC Delco 41-110 Iridiums from RockAuto. I think the plugs I had with the original rough idle issue may have been counterfeit as I got them off Amazon. In that thread someone suggested buying from RockAuto this time so I avoid that issue. That's what I did so these should be genuine plugs.

 

[Fless]

Have you looked at your short- and long-term fuel trims?

 

[Foggy]

You didn't try to "gap" them did you??? Just covering the bases this is very
abnormal. Did you replace plug wires too ??

 

[bdbull]

Have you looked at your short- and long-term fuel trims?

I have not looked at this. Honestly, I'm not sure what it is. I will see if I can view it in the Torque app.

You didn't try to "gap" them did you??? Just covering the bases this is very
abnormal. Did you replace plug wires too ??

I did not gap the plugs, but I did check them all before installing. There were all at .04. I did not replace the wires this time, but they were replaced with the last set of plugs 20k miles ago. They are AC Delco 748UU.

 

[Foggy]

Ok sounds good... Yes, don't touch the irridium gap.. Adjusting the gap in a different process
than traditional plugs and you can mess them up even checking them if not careful.

So, that being said: check your fuel trims as suggested. Make sure your oil is clean.
Make sure your Throttle body and MAF are clean as well as air filter...

Other than that, you may have an underlying issue if it is running rough after
just several hundred miles.... after a service.
I would suggest using some good injector cleaner too (like Techron) or similar

 

[Bill 1960]

How many miles on it?

What’s your fuel economy like? And looking at the fuel trims is excellent advice. Injector cleaner aka Techron if there’s any indication of running rich.

On that topic, is it getting up to temperature on typical drives, and is the coolant temp sensor working properly? Too much running cold/ enriched can be an issue.

If it’s oil, I’d do a top end piston soak to free the rings. There was a recent thread on this, if I find it I’ll update here with a link.

https://www.tahoeyukonforum.com/threads/afm-piston-soak-top-cleaner.132134/#post-1651681

 

[Fless]

Fuel trim is what the electronic systems do to maximize the air to fuel ratio by adjusting how much fuel is added at any given point in time (short-term). Target values are +/-10%, but ideal values are closer to 0%.

What Is Fuel Trim?

 

[bdbull]

Just ran some errands around town with the Torque app running. Fuel trim values seemed to stay in the +/- 10% range, although there were a few times I noticed it outside of that range.

Fuel economy hasn't seemed to change at all.

It's got a little over 213k miles on it, and most of my driving is just little quick trips around town. I work from home, so I really only go out to get the kids from school, run an errand in town, or something quick like that...usually never over about 50 MPH and probably average closer to 35MPH if that makes any difference. Occasionally I'll make a longer trip (drove 2 hours one way to pick up some wheels 2 weeks ago), but the majority of my driving is stop and go.

I'll try to pay attention to the temperature sensors next time I go out.