2007 - 2014 GM Vortec 5.3L V8 Engine AFM Fouling ~ Spark Plug Inspection & Replacement (Chevy & GMC)

[@joescott701]

Just did the plugs and wires on a 13 silverado with 97k on it. I disabled the AFM with a range technolgies device the plugs in to the obd2 port. No major change in fuel economy. Keeping fingers crossed the next 7 to 10 yrs.

[@DrShock]

Once this generation of Vortec 5.3L engines start burning oil, those Range devices are a waste of money unfortunately. The oil consumption is coming from the piston rings being gummed up from the AFM action, and by the point you detect the consumption the damage has already been done. You just have to monitor the oil consumption and stay on top of it so that you don't cause further damage from low oil levels, or replace the piston rings. Once you replace the rings, you could have AFM disabled and it _could_ be an effective mitigation then, but only then.

[@joescott701]

@DrShock I understand what your saying. The plugs I pulled out all looked good so I'm hoping for the best.

[@rickw.9298]

Where did you purchase a printed OE shop manual?

[@DrShock]

There's a link in the description where they sometimes show up used. A new set will set you back $400 or so from GMs printing partner helminc.com

[@l.m652]

2012 Chevy Silverado. Bought used at 89k. Heart sank when I first pulled the plugs, then learned about this faulty design. Stayed on maintenance, does burn oil and foils out plugs. Just changed to a new set of plugs and wires at 168k

[@johnlandry8328]

What’s the impact to the catalytic converters with oil burn?

[@DrShock]

Over time combustion of oil can _gradually_ degrade the effectiveness of the catalytic converter (or converters on those vehicles with more than one). It won't result in an internal melting/damage like pushing unburnt fuel thru will though. Just loss of effectiveness/efficiency at emissions reduction. This particular vehicle is registered in a state that still sniffs the tailpipe emissions as part of annual inspection. I'd suspect the owner would have this concern in their _don't care_ list until such an inspection fails as that's cheaper than pulling the engine to rebuild with new piston rings (the only real fix for the problem). Once these GM 5.3L engines start burning oil it's too late for any mitigation, there's nothing that will stop it short of a rebuild.

[@MrKL83]

Getting a P0300 and P0301. Checked cylinder 1 and saw oil on spark plugs. Need engine service?

[@DrShock]

P301 is a cylinder one misfire DTC, while P0300 is non-cylinder specific. Like we went over in this video, you will need to inspect all of the spark plugs for oil fouling and replace as needed as a first step. A scan tool which can display cylinder misfire data is _absolutely_ necessary to diagnose and repair the source past the spark plugs though.

[@MrKL83]

@DrShock will take out all the spark plugs and hope for the best.

[@vernwhite568]

I don’t use ac delco parts as I’ve had so many problems with them I go with makendra parts now

[@jasonhoover2590]

I did parts for quite a few years and according to the manufacturer of the spark plug you're not supposed to put a gap tool in any iridium or platinum bug because you are removing the material from the copper core. To each their own but technically you recorded yourself voiding the warranty on your spark plugs

[@DrShock]

Thanks for the comment. However, your information does *not apply* to ACDelco. The GM service manual instructs to verify the proper gap as part of General Motors authorized warranty repair procedures. The reason is simple, parts in boxes can be impacted during shipment changing the gap. The gap *must* be measured and verified before installation/usage of the spark plug into the engine, a process which causes no damage when done correctly.

[@jasonhoover2590]

@DrShock you might consider that the manual was written quite a long time back and that policies change since then ACDelco has been bought out by NGK so being that they have different owners now policies will have changed. I know that when selling them, we were informed by ngk to tell people not to gap them. And were told that if someone told us that they gaped any brand of plug we wer to not warranty the part.

[@DrShock]

ACDelco sources their plugs from several tier one suppliers, NGK is only one of them. I think I'd interpret what you're recounting here as accurate in the sense that it's encouraged to check that the gap is within factory specifications (NGK in your example). But that you return the plug for warranty replacement if it's not in spec. I believe NGK is saying do not try and _correct_ the gap yourself if it's wrong. Just return the plug(s) if it's the wrong gap for whatever reason. Thanks for sharing the detail, helpful to know.

[@jedielfsorcerer]

I have a gmc sierra 1500 5.3 L and i have p0300. Already changed sparkplug and wires months ago. And i run cleaning type of add on in the fuel tank every so often. The shop i took it to recommend a new engine, i call bs on that.

[@Oksobasically2]

I have noticed that every 1500 miles the engine burns about a quart of oil. First of all thats insane. Assuming a 5000 mile interval you lose a little over 3 quarts between changes. Thats HALF the capacity of the engine. Emissions and fuel economy have destroyed the life of these otherwise bulletproof engines.

[@DrShock]

The only real repair for this issue typically, for this particular GM engine design and model year series, is installing new piston rings. The earliest models had some service bulletins involving additional parts (revised valve cover, revised pan component, etc) which help and are all needed. But in the end even with all of those revised design parts installed, it's the piston ring design allowing oil to blow by and be combusted at a premature level of mileage on the engine. When the vehicles were still within warranty, some folks were able get their dealers to do the rings and as expected the oil consumption problem went away. But it eventually comes back (even if AFM is disabled btw). I would assert it is cheaper to just monitor the oil levels like a hawk until some other issue warrants the cost of opening up the engine. Then I would recommend doing the rings as well.