Hi guys... and I'm kinda stuck for what to do next

Fully warmed up, my 3.8 (OBD II) throws a P0300 code for misfire, on #5 cylinder, and then CEL starts flashing which worries me about the cat....

Spark plugs are good, plug wires are good, MAF checks good, EGR is good, fuel pressure is good, and I've swapped coils around & the problem stays on #5.

Problem only happens when in 'Closed Loop' operation. No misfire when engine is cold.

This is the only code that is saved

I'm new to the Camaro world, but am a retired wrench-bender from Uncle Sam's Air Circus.... Any ideas or thoughts are appreciated!!

 

Move the #5 injector see if the issue follows and compression test.

 

P0300 is a random/multiple cylinder misfire code. It's not cylinder specific, and could be pertaining to more than one cylinder.
To determine a cylinder #5 only misfire, you must have been getting a P0305 code. Just making sure you're not shooting in the dark here.

 

I should have looked that up. Moving the coil would have done nothing. Coil would be the most common issue but it could still be anything.

 

Hey guys, thanks for your ideas.

Turns out is was the coil.... cold it was fine, but as the engine came up in temp the coil would 'break down'. #5 plug was gas-fouled so a simple 60 second run after swapping coils would not show the problem as the plug had not burnt off.

Found the problem by hitting the coil with some CO2.... when cold, no problem. When the coil would warm up, misfire & CEL.

Again, thanks!