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grampoll

5.3 misfire

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I have a 2010 Sierra 1500 with 5.3 afm. It has 217000 Kms so I'm well off warranty. Anyway I'm taking the truck in for the second misfire code since I've owned it. The first one they replaced two spark plugs and installed the updated valve cover. This was at 196000 Kms. I've read lots about these being band aid fixes. Since I will be paying for repairs again what are my options? Is it too late to replace the plugs and get a tune to turn off afm? (Will the damage already be done). Or just let the dealership fix and start saving for a rebuild or trade in. Is there anything I should request they check? Maybe pull the valve cover and check valves or compression.

 

 

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It may just be time for new plugs if the remaining six are still original.

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I had a misfire that turned out to be a plug wire. I checked them with a meter as I pulled each one off and they were all similar readings. But a meter is DC and does not check a wire completely like during operation. Once all the wires were changed, the misfire went away. I have also seen a coil cause a misfire. I never did figure out which wire it was.

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Just an update. I took it into the dealership to get checked out. They said there was oil found in the intake and all they could do was the chemical clean for $1500 and it's not a guarantee fix. They recommended finding a used engine to swap. They put a new plug in cylinder 7 and gave it back to me. Since I got the truck back I have been driving in m5 and putting it in 6th on the highway. 1000km later it hasn't burnt a drop. Going in for a tune next week.

 

 

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The most important thing is to get a tune to turn off the AFM function (the AFM switches from 8 cylinders firing to 4 cylinder mode, supposedly to save a little bit of fuel). Then you'll want to install a catch can in your PCV system. Check with your dealer to make sure your truck came from the factory with the revised oil deflector in the oilpan and the revised driver's side valve cover (it has a relocated and resized PCV orifice), or has had them fixed since then. Get new spark plugs installed and run some AutoRx or equivalent in your oil to help clear your stuck oil rings on your pistons. And occasionally run some Techron Fuel System Cleaner or equivalent in your gas to keep your new spark plugs from getting oil fouled. All of these items have been covered in this forum and can be found doing the search function. If you do all of this, your truck's oil usage will probably drop 95% and it will run better. But I've been told that some of the 07-13 trucks still have a more 'nervous' idle than we have been used to in the past, due to the cam, lifters, timing, and firing order being changed due to the AFM system.

 

I don't know what your dealer would be charging $1500 for, unless it would be installing the revised GM parts for the valve cover, oilpan deflector, and doing a piston ring cleaning treatment.

 

 

Just an update. I took it into the dealership to get checked out. They said there was oil found in the intake and all they could do was the chemical clean for $1500 and it's not a guarantee fix. They recommended finding a used engine to swap. They put a new plug in cylinder 7 and gave it back to me. Since I got the truck back I have been driving in m5 and putting it in 6th on the highway. 1000km later it hasn't burnt a drop. Going in for a tune next week.

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Edited by Maverick Z71

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