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.

 

[Foggy]

Good idea... watch your actual coolant temps.. The gauge is OK at best..
180* - 215* all shows up on these gauges at the 210* middle mark.. So don't trust it.

Short trips are not great... Oil does not get up to temp and gets dirty and full of moisture
very quickly... I'd do an oil change and add a catch can. Then drive for a several hundred miles

 

[bdbull]

Good idea... watch your actual coolant temps.. The gauge is OK at best..
180* - 215* all shows up on these gauges at the 210* middle mark.. So don't trust it.

Short trips are not great... Oil does not get up to temp and gets dirty and full of moisture
very quickly... I'd do an oil change and add a catch can. Then drive for a several hundred miles

Went into town today and the temp got up to a normal range. It was right at 210 on the gauge and the Torque app had it right around 194. Just checked my coolant and it appears to be a little low. I wonder if I have a coolant leak and that's what's causing the plugs to get dirty. I've read/watch Youtube videos before on testing for a coolant leak but I'll need a refresher if I decide to check that out.

I have a catch can on order, but probably won't get to it until this weekend.

Oil was changed about 1500 miles ago when I did the AFM deflector and oil pan gasket.

 

[bdbull]

Made a couple updates since I first posted. Installed the updated driver side valve cover with an oil change. (That was a whole other adventure.) Just installed a catch can as well. Will be out of town for the next few days in my wife's Tahoe so won't get to drive my truck until next week, though.

 

[bdbull]

Put about 150 miles on it with some interstate driving and everything seemed normal. The rough idle seemed to be a little better, or I could have just been hoping it was better. But, just when things seem to be going well, the proverbial hits the fan.

Coming back from an appointment across town just now and all of a sudden traction control and stabilitrack lights go nuts. Truck seemed to be driving fine at highway speeds, but lower speeds were very rough. I made it home and popped the hood to see if I could see anything obvious. Sounded like there might be a vacuum leak or something leaking air, but I couldn't tell for sure. Unfortunately my bluetooth OBD reader is in my wife's car so I can't check the codes until she gets home. Once the engine cools down, I may go remove the catch can and replace it with the OEM PCV hose to see if the "air leaking" sound goes away. Hopefully it's just that simple, although I don't know why it would work for a few hundred miles and then all of a sudden not.

Hopefully it's not related to the valve cover work that was done recently.

It never freaking ends.

 

[Geotrash]

Put about 150 miles on it with some interstate driving and everything seemed normal. The rough idle seemed to be a little better, or I could have just been hoping it was better. But, just when things seem to be going well, the proverbial hits the fan.

Coming back from an appointment across town just now and all of a sudden traction control and stabilitrack lights go nuts. Truck seemed to be driving fine at highway speeds, but lower speeds were very rough. I made it home and popped the hood to see if I could see anything obvious. Sounded like there might be a vacuum leak or something leaking air, but I couldn't tell for sure. Unfortunately my bluetooth OBD reader is in my wife's car so I can't check the codes until she gets home. Once the engine cools down, I may go remove the catch can and replace it with the OEM PCV hose to see if the "air leaking" sound goes away. Hopefully it's just that simple, although I don't know why it would work for a few hundred miles and then all of a sudden not.

Hopefully it's not related to the valve cover work that was done recently.

It never freaking ends.

Sure sounds like an intake manifold leak to me. I'd yank that thing out and check for cracks, then put it back on with a new gasket set if none are found. You can do the whole thing in 2 hours or less. You can put a new oil pressure sensor and screen in while you're in there. And you can take that stupid plastic piece at the back of the manifold that makes changing the oil pressure sensor such a PITA, and throw it in the trash.

 

[bdbull]

Checked all plugs and wires, everything seated properly. Changed back to the OEM PVC hose. The hissing sound was gone but the truck was still running like crap. I've seen a few videos where a catch can produces a hissing sound because of the hoses used so I'm guessing that's what's going on there.

Sure sounds like an intake manifold leak to me. I'd yank that thing out and check for cracks, then put it back on with a new gasket set if none are found. You can do the whole thing in 2 hours or less. You can put a new oil pressure sensor and screen in while you're in there. And you can take that stupid plastic piece at the back of the manifold that makes changing the oil pressure sensor such a PITA, and throw it in the trash.

I'm just a YouTube mechanic so I have no clue about the intake manifold. I'll search on YouTube for videos on that, but if you have any offhand that'd be great. As for the oil pressure sensor and screen, I've changed those at least 4 times now so I'm pretty familiar with that job. (Thanks GM)

 

[Geotrash]

Checked all plugs and wires, everything seated properly. Changed back to the OEM PVC hose. The hissing sound was gone but the truck was still running like crap. I've seen a few videos where a catch can produces a hissing sound because of the hoses used so I'm guessing that's what's going on there.

I'm just a YouTube mechanic so I have no clue about the intake manifold. I'll search on YouTube for videos on that, but if you have any offhand that'd be great. As for the oil pressure sensor and screen, I've changed those at least 4 times now so I'm pretty familiar with that job. (Thanks GM)

I don't have any YouTube videos for it, but I'm sure they're out there. There's really no trick to it. The only PITA is getting the fuel rail separated from the hose, but all you need to do it in 30 seconds is to drain the pressure in the fuel rail using the Schrader valve on the passenger side of the fuel rail, and to use the right GM quick connect line tool on the fitting itself. Easy peasy.

 

[bdbull]

Wife got home with the code reader so I checked it out. Only code it has is P0300 so not much help there.

Been watching a lot of videos about stuck lifters due to high mileage and AFM so I decided to take a look. No stuck lifters on the driver side. But...of course when putting the valve cover back on one of the non-stripped out bolt holes from my previous issue stripped out as I was torquing it down. So, I'm throwing in the towel and taking it to the shop in the morning...the same shop that already fixed the first two stripped out bolt holes. Gonna cut my losses and not even attempt to look at the lifters on the passenger side. FML

 

[Caligirl]

Following 'cause we are dealing with VERY similar crap with our 2007 Tahoe. Also do short drives that barely warm anything up. We are just starting down this rabbit hole, so will share what we findas we go. Already had vacuum test and fuel trim readings done... plugs the next project because our mechanic friend thinks plugs, wires, coils may be issue (but WHY did they fail so soon?). Husband was gonna do them himself, but not like older trucks and needs special tools or hands that can turn into stretch material to get into little tiny areas...

 

[bdbull]

Does this offer any useful information? I don't know what this might mean other than it thinks there's something wrong in the fuel system, whatever that means.