1997 cadillac deville- misfires on cylinder #1 when cold and starting up, and also when hot and left off for a few minutes, and then restarted. Runs rough for 15 seconds or so, and then the problem goes away, except an occasional service engine soon light hard code saying misfire on cylinder #1. Spark Plugs, Wires, and a coil pack for cylinder 3 and 8 was replaced already to address missing in the cylinders 3 and 8. Also, the #2 O2 sensor replaced because the code for slow oscillation came up, previously. Also, after the above parts were installed, the next day, a sweet smelling antifreeze kind of smell and fog came out of the tail pipes. So, I dumped some $32 cylinder head gasket seal from Advance auto into the upper radiator hose and crossed my fingers. So far, the vibration after starting it up hasn't returned and the SES light hasn't gone on again after trying the head gasket seal. I wonder if the head gasket seal stopped a tablespoon or so of antifreeze from entering the cylinder #1 when I shut the car off running hot, and also, leaving it over night after running it hot? Is it possible that the antifreeze leak can cause an initial miss?

By the way, found in the service manual that a misfire condition can be caused by secondary spark plug wires routed too close together on the right bank of the engine. So, I purchased some spacers from Advance Auto Parts, and the miss went away, luckily. Apparently, cylinders 1 and 3 should be separated at the boot for cylinder #3, and at cylinder #5, the #5 boot should be kept as far away from spark plug wires that lead to cylinders #1 and #3. It's okay to keep cylinder #1 and cylinders #3 wires close together at the cylinder #5 boot. Anyway, there is a diagram in the manual for the Northstar 4.6L engine that I found online through my library that details this. By the way, found in the service manual that a misfire condition can be caused by secondary spark plug wires routed too close together on the right bank of the engine. So, I purchased some spacers from Advance Auto Parts, and the miss went away, luckily. Apparently, cylinders 1 and 3 should be separated at the boot for cylinder #3, and at cylinder #5, the #5 boot should be kept as far away from spark plug wires that lead to cylinders #1 and #3. It's okay to keep cylinder #1 and cylinders #3 wires close together at the cylinder #5 boot. Anyway, there is a diagram in the manual for the Northstar 4.6L engine that I found online through my library that details this.