I recently bought a 2008 Silverado 5.3 with 77k on it. After a couple weeks I noticed that at idle the engine would stumble and my rpms would drop slightly. It eventually set off the check engine light with cylinder 1 misfire and random cylinder misfire. A couple days later the light went off but the issues remain.
Since then I've cleaned the MAF with MAF cleaner spray, cleaned the throttle body, and run a couple bottles of techron through to clean up the injectors, but no change.
I dont know if it's related, but I also get a lot of dark blue/black (hard to say) smoke from the tailpipe on cold starts for a few seconds before clearing up. This led me to thinking I was getting oil in the cylinders when the rings cool and contract, which I tracked to known oil burning issues with these AFM engines.
At this point I'm not sure what else to try before spending a fortune at the shop. My only remaining thought is to replace the plugs and coils. But even if that fixes the misfire I'm not sure what to do about the cold start smoke.
EDIT: I had been keeping a casual eye on my oil levels since my last change and did notice a pretty drastic decrease in just a couple thousand miles. I'll just changed it again this past weekend and will keep a close eye on it. Would this affect engine misfires?
EDIT2: I pulled the #1 cylinder spark plug since I had a misfire code for that cylinder and it was fouled up with oil and deposits in the threads and at the firing end.