Dreaded P0300
Dreaded P0300 Truck is an '04 Hummer H2. Ive only had a short time. When I test drove it, everything worked great, ran great, etc.
Being a new to me vehicle I changed all the plugs, wires. I went with AC Delco wires and had NGK TR5GP plugs. The truck ran like crap and I was getting the code above. I swapped in AC Delco cheap copper plugs and it runs a lot better. No more code if I stay out of it. But if I floor it, or add any real throttle the check engine light blinks and the motor stumbles. I have Torque, the program for the Android, so I can read the codes and see some parameters. Ill try to log as much as I can and figure out how to post them.
But driving it today I had an idea. I parked the truck, left it in Park, and floored it. No code, no CEL flashing, no stumble, nothing. Revd great all the way up to 5500-6000 before I let off.
I do have some mechanical knowledge, but I am mainly an LT1 guy from my old Camaro.
Reading around online, it seems the P0300 is a misfire that could be cats, coils, lifters, plugs, etc. But I am wondering why wouldnt it break up while in Park?
Any ideas? Thanks.
Being a new to me vehicle I changed all the plugs, wires. I went with AC Delco wires and had NGK TR5GP plugs. The truck ran like crap and I was getting the code above. I swapped in AC Delco cheap copper plugs and it runs a lot better. No more code if I stay out of it. But if I floor it, or add any real throttle the check engine light blinks and the motor stumbles. I have Torque, the program for the Android, so I can read the codes and see some parameters. Ill try to log as much as I can and figure out how to post them.
But driving it today I had an idea. I parked the truck, left it in Park, and floored it. No code, no CEL flashing, no stumble, nothing. Revd great all the way up to 5500-6000 before I let off.
I do have some mechanical knowledge, but I am mainly an LT1 guy from my old Camaro.
Reading around online, it seems the P0300 is a misfire that could be cats, coils, lifters, plugs, etc. But I am wondering why wouldnt it break up while in Park?
Any ideas? Thanks.
