[ACRobb]

Hello, I could use some ideas on how to troubleshoot my car. It has a solid check engine light with codes:
1. P0300 “Random / Multiple Cylinder Misfire Detected”
2. P050D “Cold Start Rough Idle”

Here’s a description:
-Initial crank starts around 1.2k RPM then after ~30 seconds it drops to normal around 600 RPMs. Shows solid check engine light but acceleration feels normal.
-This happened before but had a flashing check engine light with a stabilitrack light coming on as well. I heard an unusual noise (sorta like whining) from the engine and it felt sluggish when accelerating. I cleared the code and the issue went away for a day or two (except for the high initial idle with cold starts).
-I have replaced the spark plugs, coils, and wires. Before I did this it gave off codes P0308 (cylinder 8 misfire), P050D, and P0128 (coolant thermostat).

The next step is a compression test. I’m open to other suggestions.
2016 Camaro 2SS, automatic, 68k miles, and is stock.

[Patriot Motorsports USA]

Also do an oil test and see if you are getting fuel in your oil. Couple this with a leakdown and see if the cylinders showing the misfire, are the ones showing low compression or an inability to hold pressure.

Which plugs did you use?

[bishopts]

Look at live data and check individual cylinder misfire numbers.
Look at your spark plug wires where they are closest to the exhaust manifold and make sure they aren't discolored or cracked.
Look at fuel trims to compare bank 1 vs bank 2 to help figure out what side its happening on.
Make sure you didn't crack the porcelain on the plugs when you put them in.

[ACRobb]

Originally Posted by Patriot Motorsports USA

Also do an oil test and see if you are getting fuel in your oil. Couple this with a leakdown and see if the cylinders showing the misfire, are the ones showing low compression or an inability to hold pressure.

Which plugs did you use?

NGK Spark Plugs “Iridium IX”
MSD Ignition Coils
MSD Black SC Wire Set