1972C10

Sorry, that was a typo on the ignition coil swap. Should have been cylinder 5 instead of 4 (OP edited). I'm wondering if the previous owner replaced a bad lifter but didn't replace or inspect the cam for damage. Valves did appear to be opening the same amount on 5, but that was also in park on a cold engine. I'm getting misfires in drive at idle. Updated the post with code definitions. I think my next step I'll do a compression test. If that checks out and nothing abnormal, then I'll inspect the intake gasket and run a can of seafoam through it. Today while driving to work it was misfiring but not as bad. Not enough to throw a CEL or store a code. It's odd how random it is.

I'm new to the forum and looking to get some advice and next steps on an issue I'm having. Specs: 2010 Chevrolet Silverado 1500 - 6.2l - 124k miles Issue: I'm having a misfires on cylinder #5, only at idle and when in drive. It will not misfire when in park or when accelerating. The misfiring seems to be a bit random meaning it'll misfire sometimes and other times it'll be bad enough that I get a blinking check engine light, traction control light and stabilitrack service warning. All warning lights will turn off after about 15 seconds or when I accelerate. The other thing I noticed is the truck begins to misfire about 3-5 seconds after coming to a complete stop and idling. Codes that it's throwing (using a veepeak OBD scanner): P0300 - Random/multiple cylinder misfire detected P0305 - Misfire cylinder 5 P2270 - Heated oxygen sensor (HO2S) 2, bank 1 - signal stuck lean C0561 - System disabled information stored engine speed out of range; system disabled information sotred acceleration pedal position out of range; system disabled information stored transmission gear invalid data. What I've done so far: Switched spark plug from cylinder 3 with cylinder 5. Misfire still exists. Switched spark plug wire from cylinder 3 with cylinder 5. Misfire still exists. Switched ignition coil from cylinder 3 with cylinder 5. Misfire still exists. Replaced fuel injector on cylinder 5. Misfire still exists Pulled the valve cover off and observed for a stuck lifter. No stuck lifter. Started engine to verify lifter worked. Lifter worked. Cleaned MAF sensor just in case. Misfire still exists. What should be my next steps in diagnosing this issue? I'm thinking compression test. I also have a feeling it could be the intake manifold gasket that is leaking. This is a truck I recently acquired and do not know the service history on it outside of the spark plugs being replaced in the past 10k miles.