2.9 ticking/tapping sound after compression test performed
 

First just wanted to say I've been reading here awhile and finally started an active account. Hope to be able to contribute where possible.

For now, I have a question I hope someone has come across before.

2000 S80, 2.9L. Was running good, but I have a coolant issue that I wasn't sure if it was the overflow tank letting in air or the engine, so I pulled the coils and plugs and ran a compression test. Compression was fair, 145, 140, 130, 120, 120, 140 or so. Nothing too alarming. So I put the spark plugs back in, coils back in, hook it up, and after firing it back up the engine is ticking / tapping. I double checked that all coils are seated good and that they were hooked up to the proper wires. I believe #5 is the one that has the electrical feed towards the firewall.

If I unplug each coil pack, the engine responds accordingly with sluggishness, indicating that every coil/plug is firing.

Any ideas on what could have gone wrong here?

My steps for compression test involved unplugging all coils so the engine would not fire. Could this have harmed ignition in any way? I had forgotten to kill the fuel.

Hoping timing did not slip.

Thanks for any tips or guidance.

Still baffled how pulling the plugs and cranking the engine over caused the engine to start sounding like a diesel. No low oil pressure indicator either. Little nervous about playing with timing, I've only worked on non-interference before.

Assuming my oil may have gotten a bit fuel diluted for my forgetfulness in disconnecting the fuel, I'm going for a fresh oil change tomorrow.