P0300 Nightmare is back

[itratis]

Driving about 60 mph I'm getting the CEL P0300. AGAIN!!!!!


Here is the Freeze Frame data:


DTC for which Freeze Frame was Stored - P0300
Fuel System 1 Status - Closed Loop
Fuel System 2 Status - N/A
Calculated LOAD Value - 50.6 %
Engine Coolant Temp - 183 °F
Short Term Fuel Trim - Bank 1 - -2.3 %
Long Term Fuel Trim - Bank 1 - 3.9 %
Intake Manifold Absolute Pressure - 15.5 inHg
Engine RPM - 2,330.00 rpm
Vehicle Speed Sensor - 57 mph
Intake Air Temperature in degrees F. - 88
Spark Advance - 33
Absolute Throttle Position - 18.4 %

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Items replaced:
Spark Plugs - Cables - Coil - Catalytic Converter - Air Filter - Oil - Oil Filter - New Battery

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Applied Procedures:
CKP Crankshaft Variation Relearn
2 cans of fuel injector cleaner
Cleaned EGR Valve
Replaced any worn vacuum lines
Cleaned Intake Resonator

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I do not want lose my faith on Chevys but........ well searching for a solution, I have red that some times the problem are the spark plugs, injectors, Vacuum leaks and some exotic things like a "serpentine belt slap"

Any more suggestions based on the freeze frame data?

[xintersecty]

You have done it all. Is there any oil on your plugs? Did you check your valve cover gasket for leaks? I would make sure your grounds are all good between the coils and battery.

[itratis]

Did remove the spark plugs, all dry, valve cover no leaks, got under the car to check ground connection next to the starter, seems to be ok.

I do not know what to think since the random misfire occurred most at about 2300 RPM, may be a defective Idle Pulley?

[xintersecty]

That is a good guess on the idler pulley. The Ground you want to check is next to the battery access from the top.