2006 GMC Sierra 1500 weird P0300 codes

[Tantrix]

Ok so one day when the wife and I were coming home from a restaurant, when I started the truck I had a code.  So, I get my scanner out and it shows a P0303 code, which is a misfire on cylinder 3.  Well, on the way home when going up a bridge the truck starts cutting out just like a misfire.  Fast forward and I check all the ignition coils and all come out good.  So, I had my plugs and plug wires changed but made no difference.  Finally, I brought it to my local shop here and after testing it repeatedly, gives me the bad news...I need to have the heads pulled, polished, and a new gasket.  Well, about a week later I get it back and no more misfires.  Ok, good to go.  Then...

 

One day it's cold outside and I've got the truck warming up and I rev it a few times before pulling out of the driveway and I get a code flashing then going out.  I get out my scanner, and it shows P0300 this time (random misfire).  I clear the code and drive on, and it never happened again.  When I got home I put the truck in neutral and held the throttle at about 2200 RPM and within 5 seconds it throws the P0300 again.  The truck is not missing and runs fine.

 

 

Has anyone else ever heard of just being able to sit in neutral at 2200 RPM and get a P0300 every single time?

[utah33]

I had a p0300 I fought for a year. After replacing all the O2 sensors, the crank sensor, spark plugs & wires what ultimately fixed it was the fuel injectors need a professional cleaning. After I got the injectors cleaned the code has not returned. It has been several months now. This was on a 2002 5.3L Silverado.

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