Chev 5.3L P0300 code

[LundExplorer]

Airjer and other "gearheads", need some help.

I have a 2000 Chevy Silverado, 5.3L V8, 123,000 miles. I'm getting a P0300 code (Multiple random misfire) occasionally - ONLY the P0300 code and no others.

If I hold the engine at 2500+ rpms (in park) for about 20-30 seconds I will get the Service Engine light and the code. I also get the code out on the highway very infrequently, but it will happen often if I am towing a trailer.

There is nothing noticeably wrong going on with the engine, I do not feel a misfire during SES light flashing or after it is on constant, gas mileage is normal, engine runs as it always has.

Last spring is when I first had this happen, along with another code that pointed me at the throttle position sensor. I replaced this and the plugs & wires. I do not get the throttle position sensor code any longer, just the P0300. I have replaced the air filter and have cleaned the MAF sensor & still get this code.

Any ideas? The SES light is annoying and I don't want to just start replacing parts that may not be the problem.

Thanks!

[Jeremy airjer W]

Your best option is to get a good high end scan tool on this and check misfire history. I will put money on it being a specific set of cylinders causing the misfire and more specifically one bank or the other. either 2-4-6-8 or 1-3-5-7

What brand of plugs did you put in it?

[LundExplorer]

Airjer, thank for the reply. I am running AC delco plugs as recommended and they looked good. I took your advice and brought it to my neighbor mechanic who had a scan tool and saw that misfires were on all cylinders with 1 and 6 having most. So we changed the fuel filter and that solved it, at high eng speed it was lean misfiring, just enough to set a code and blink the light. This could have been a very expensive problem as there are multiple causes for this code. Fortunately a fuel filter and 2 hrs mechanic labor was all it cost. Thanks for helping save me some $$$$.

[Jeremy airjer W]

Definitely not what I was thinking but resolved (cross your fingers) non the less!

[1968]

That's a strange one. I would expect a filter plugged enough to cause a missfire would have also set lean codes and probably some hard starting.

Also, a filter that plugged will have shortened your fuel pump lifespan.

[LundExplorer]

Thanks, guys. I just ran it up north pulling a trailer, and no Check engine light at all. I'm keeping my fingers crossed on the fuel pump. Pump output looked good according to my mechanic. It's the 2nd pump on this truck, time will tell.