I will on occasion get this code, but only under these circumstances. First off the vehicle in question is a 1998 GMC Sonoma w/ 4.3 V6. If I am at interstate speeds and I really put my foot down on the gas pedal, it will throw the code or same circumstance, but going up a steep incline (like going to the mountains) it will throw the code. I have had it scanned and it is still within the parameters of the manufacturer. It has 174,000 miles on it and runs perfectly fine except under these circumstances. Even a fresh tune up doesn't change anything. What could be the issue? I'm just curious to see if there is something that I can do. Thanks.
Just saw the tag for P0300, is that the only code that’s showing up?
Change your fuel filter & pressure test the fuel pump & check if the readings are within spec.
For further diagnosis, have a read through this -
https://carkiller.com/scottykilmer/qa/misfire-4/
since it only happens under high load, I would suspect the dizzy or fuel pump.
Fuel filter has been replaced. Will have the fuel pump checked. Thank you!!!