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P0300 Fault Code in 1996 Chevrolet Camaro 3.8L: Diagnosis and Next Steps

Model: 96 camaro 3.8 Fault Code: P0300 Posted: 2014-03-06 21:52

I'm experiencing a persistent P0300 misfire code on my 1996 Chevrolet Camaro with the 3.8L engine. The scan tool indicates significant misfires in Cylinder 6, approximately half as many in Cylinder 4, and no misfiring in any other cylinders. I've already replaced all spark plugs, plug wires, coil packs, and the ICM. Fuel pressure checks show consistent readings at 47 psi with only a 2 psi variation during acceleration; vacuum system tests reveal no leaks, and a new PCV valve has been installed. The misfire symptoms begin about 20 to 45 seconds after starting the vehicle when cold and persist even after the engine warms up. The issue worsens when the car is shifted into reverse or drive while parked. A gasoline odor becomes noticeable after running for several minutes. I'm seeking advice on what steps to take next to resolve this issue, especially since all standard components have been replaced. I've also confirmed that my scan tool provides live data and no additional P1xxx fault codes are present.

Related fault codes
P0300
Comments (4)
Anonymous 2014-03-07 09:51

What is your exact fuel pressure reading in PSI? Does your scanner provide real-time live data and detect any P1xxx fault codes? Were the replacement spark plugs all AC Delco? Did you perform a fuel pressure leak-down test during your inspection? Did you conduct a compression test on cylinders 6 and 4? These details are critical to determine the next diagnostic step.

Anonymous 2014-03-07 12:12

Probably best to do a injector drop test. To rule out restricted or dirty injectors. Need special equipment or a scan tool withthe capability With a fuel pressure gauge. Maybe switch injectors around and see if misfire follows. Could try some techron total fuel system cleaner available at autozone.

Anonymous 2014-03-07 16:39

Thank you for the helpful suggestions—I plan to follow through with these steps and will update my progress in a few weeks when I'm able to work on the vehicle again. The spark plugs were all AC Delco. Fuel pressure remains stable at 47 psi, fluctuating only about 2 psi during acceleration, and passed the leak-down test. My scanner does provide live data, but no additional fault codes (such as P1xxx) are detected.

Anonymous 2014-03-08 11:43

You performed a leak-down test with the key on, engine off (KOEO). For accurate results, this test should be conducted with the engine in the 'run' position, not just key-on, engine-off. This ensures proper pressure retention and more reliable diagnostic data.