P0300 Fault Diagnosis for 1998 Chevy K1500 4.3L V6 - Misfire at High Speeds
I own a 1998 Chevrolet K15-00 with a 4.3L V6 engine and am currently experiencing a noticeable hesitation or misfire when cruising above 65 mph. The vehicle runs smoothly at lower speeds and during acceleration, but the P0300 diagnostic code appears consistently under high-speed conditions. I've already replaced the spark plugs, plug wires, distributor cap and rotor, and the fuel filter. Fuel pressure testing showed readings just within acceptable limits—on the low side of specifications. One mechanic suggested checking fuel volume (not pressure), which I have not yet done due to difficulty finding a service provider who performs this test. A local garage recently diagnosed an unplugged MAP sensor, recommending reconnection as a fix. However, after this repair, the issue persists. I plan to return to that shop on Monday for further evaluation. If anyone has experience with P0300 misfires in 1998 Chevy K1500 4.3L V6 models or knows potential root causes—especially related to fuel delivery or sensor issues—I would greatly appreciate your insights. Thanks in advance!
Given that the fuel pressure is on the low side and the filter appears dirty, it's worth inspecting the fuel tank pickup tube screen. In some GM vehicles, including this model year, there are two screens located within the fuel pump assembly—both of which can become clogged over time and contribute to poor fuel delivery and misfires.