Heres the short version:

6 weeks ago, P0302 popped up along with some others related to cylinder 2. Replaced #2 fuel injector with 6 new lower o-rings on all injectors. Problem solved at the time

Yesterday, changed UIM and LIM gaskets. Found that coolant had been leaking into cylinder 4 and 6 intake ports resulting in misfire and coolant in the exhaust. Also changed out spark plugs on 2,4, and 6 due to missing electrode tips.

Results, no more steam/smoke from exhaust or leaky gaskets. Now the P0302 code popped back up. Checked new injector inpedence, 13.6 Ohms
Spark Plug is brand new as of yesterday
Even bought new spark plug wires yesterday
Checked primaries on coils, they are within specs according to BF tech info threads
I even swapped 2 coils packs around just to see what would happen.

Still has misfire on cylinder 2.

Checked the wiring and voltage coming from injector 2 wire harness. One side has 13+ volts.

WIll be ordering a fuel pump only on Friday to see if it remedies the problem. Pump has been giving the "whine of death". If the fuel pump were going out, would it only affect cylinder #2?

If anyone has any ideas I haven't tried, please chime in.

check the inj connector see if the wires going into the connector are loose. or the connector itself

OK, you swapped coil, no change, new wires, no change, new plug, no change. I have seen a bad ICM effect a cylinder. But it should effect 2 cylinders because this is a waste spark system. Options now are to swap 2 injectors and see if the problem follows the injector. If not, you have removed just about all your options. Your getting in to mechanical problem area. Pull the valve cover and inspect the valve springs. I have seen 2 engines now with odd misfire and they passed every test I threw at it. Wasn't until I inspected the springs that I found the problem.

Okay, here is what I have so far in the last couple of days.

Replaced original fuel pump with new one from Rock Auto. I knew the old one was getting weak due to the "GM dying fuel pump whine". No change, cylinder 2 misfire,

Swapped #2 and #4 injector harnesses, no change.

Took ICM to O'Reilly and tested bad, put in new ICM...cylinder 2 misfire. Had O'Reilly test the new replacement ICM, tested bad. Had them test another new ICM from another brand, tested bad. Their machine is bad. Put old ICM back on, no change. Cylinder number two misfire.

Swapped brand new spark plug from #2 with older plug #5. MISS WAS WORSE...I had changed 2,4, and 6 plugs a couple of weeks ago when I changed UIM and LIM gaskets. Only 4 and 6 had coolant in the intake ports though. I decided to change that bank of plugs because one of them had the electrode blown off. Can't remember which cylinder that damaged plug came from though.

I even checked to see if I swapped 2 and 4 plugs wires if that would do anything. No change..cylinder number two misfire.

I also checked the primaries and secondaries on the coil packs, all within spec. Swapped two of the coil packs around, no change.

I will run a comression test on it hopefully tomorrow to see what might be happening.

If it is a spring, I think I can swap that out. Will be a PITA though. If it is a head gasket or piston/ring related, I'm screwed.

Any other advice would be greatly appreciated. Oh yeah, I'm going to swap the #2 and #1 injectors around to see if that does anything.

When you found that the springs were bad, which were they? I have the tools to swap out valve seals on a tradition GM V8 engine. I've never attempted anything like this on a FWD engine on the rear banks of cylinders. Is there a thread related to this task?

Appreciate all the help!!!

You mention a damaged plug. What was damaged, was it smashed? If so, this indicates a chipped piston. A chip can cause all kinds of problems depending on what all happened. Could have damaged a valve. Do a compression test, this will tell you if you have a damaged valve or blown head gasket. But won't tell you if you have a bad valve spring. Only a visual inspection will show this. A chipped piston can only be found by using a bore scope.

I have this write up. https://www.gmforum.com/performance-137/installing-new-valve-springs-rockers-pushrods-278815/ Should help a bit. Changing a spring is like changing any other spring. If you have done a V8, it'* the same. Only problem is the rear head is very tight.

I'll see if I can find some threads for you to look at.

https://www.gmforum.com/showthread.p...=broken+spring

https://www.gmforum.com/showthread.p...=broken+spring

https://www.gmforum.com/showthread.p...=broken+spring

The spark plug in question had about 2mm of the metal tab above the electrode missing. Wish I still had the plug to take a picture.

In regards to the first thread, do these engines require you to set the valve lash like traditional V8'*? I've never had to potentially go this far into one of these engines. If this doesn't apply to this type of valvetrain, do I simply apply the proper amount of torque to the rocker arm bolt and go on with Life? If so, whats the proper torque setting?

Have you ever come across an inmproperly sealed UIM and LIM gasket that would cause a cylinder 2 misfire? Maybe a strange vacuum leak just in that corner of the manifold mating surface? Sorry for the 72 questions, just running through all the options. Thanks for the guidance!!!