P0300 Nightmare is back

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


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?

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.

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?

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