OldSchoolFormula

Driving the Z06 today, steady speeds and the check engine light started flashing continuously. Slowed down, car was obviously missing and bucking. Felt like it was running on only a couple of cylinders. Felt the exhaust pulses out the tail pipe, drivers side was cold. Noticeable heat difference between the two outlets. Babied the car home and started diagnosing. When I put a timing light on the plug wires, I get a reading off every cylinder except number five. I have swapped coil packs around with my other LS1, swapped coils between the packs themselves, no change. Changed plug wires, changed spark plugs. Still no fire on number 5 according to the timing light. If I setup a plug wire and plug and ground it to the frame, I can visually see a spark coming off the electrode for number 5, so it is firing. However, while visually watching this, the timing light is not picking it up. Tried the same with number 3, grounding it to the frame and I can see the spark and the timing light picks up the signal. Odd. Also curious about what is going on with the MAP code - is it possible or likely that I am throwing this code due to the misfire? That would cause erratic vacuum readings.

Absolutely stumped with this one and still not sure why the exhaust is cold on one side if 3 cylinders are still firing. Help would be greatly appreciated....

OldSchoolFormula

Broken intake valve spring. Bone stock LS6. Weird that it happened after the car was all warmed up and just putting around. It wrapped itself luckily so as to not drop the valve.