Cadillac STS Forum - 2005 through 2012 Discussion, Help with 2005 STS misfire P0304 in Past Cadillac Vehicle Discussion; I've got a reading on my CarMD of P0304, cylinder 4 misfire. I've searched through this forum and it appears ...
I've got a reading on my CarMD of P0304, cylinder 4 misfire. I've searched through this forum and it appears the consensus is that the plugs should not go bad before 100,000 miles. I've got 76,000. I am assuming that the coil pack that connects to the plug may have a bad connection or gone bad.
Sometimes it is very obvious that there is a misfire. Shaking, bad acceleration. I can hear and feel it. Then other times I'll start it up and it is as smooth as can be. Today while coming home, it started out smooth and then started shaking again.
I'd like to take off the engine cover so that I can access the plugs and wires. If I read correctly, I just need to remove the caps and yank it off. Also, how do I know which cylinder is which?
I think it does vary with the damp weather as I am in the Albany, NY area and we have had a bit of rain this week. It was worse in the morning and then after the engine was heated it would smooth out. The only exception to that theory is today. It was bad in the morning and very damp. The engine smoothed out and was fine when I drove at lunch. After work, it was very humid and started smooth then started shaking a few miles out.
Here's the latest. Replaced plugs, ignition coil on both #3 and #4 and also injectors for #3 and #4 (All AC Delco OEM). Still getting the same codes. Noid test failed on these 2 connectors on the harness.
Should I look to replace the harnes or could this be a problem with the ECM?
Also, does anyone know the part number for the fuel injector wiring harness? I have searched everywhere and can't find it.