Hello everyone.
I have a 2007 Avalanche LT 5.3 that has a rather substantial misfire at idle that will go away if I raise the RPM to 1500 or more. If I let it idle long enough, the MIL will start flashing, which will stop flashing with increased RPM. The misfire happens mostly with cylinder #4 but sometimes with #6. This is what I have done so far, new spark plugs and plug wires. Short term fuel trim was a little high at time on bank 2, up to double digits, so I decided to replace the intake manifold gaskets which did improve the numbers. There is an intermittent lifter tick. I swapped coils around to see if the misfire would follow, it didn't. Could this be the infamous DOD/AFM faulty camshaft/lifters issue and, if so, why only at idle? It can handle a highway trip all day long with no issues with the cylinder shutdown happening as it normally should with no drama. Could it be an oil pressure issue, with "iffy" lifters pumping up better at higher RPM? I am not afraid to do the work if worse comes to worse. I have the skill set, experience, tools and workspace to do the job myself if necessary but it will still be a minimum of $1000 in parts but I want to be sure first. I am running 5W30 Mobil 1 oil.
Any ideas? Thankyou all in advance for any suggestions.

 

First I think you should use a better quality oil filter. Does the Fram have an anti-drain back valve ? Your 5.3L requires that. Second I’d check the fuel injector. Last the oil pressure. Hope you figure it out. PS a good scanner could help with live data.

 

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