TIL cleaning spark plugs on a Continental IO-550 saved me 4 hours of troubleshooting

I've been working on this Cessna 210 for three days trying to figure out why it was running rough on the right mag. Checked timing, swapped harnesses, even pulled the mag and bench tested it. Nothing changed. Yesterday I finally decided to just pull all six spark plugs and clean them with a wire brush and some brake cleaner. The difference was insane. Went from a 150 RPM drop to maybe 20 RPM drop on the mag check. I guess the previous mechanic wasn't using anti-seize and they were just caked with lead deposits from the 100LL. Now I'm wondering how many other times I could have saved myself a headache by starting with the simplest thing. Have you guys ever spent way too long chasing an issue that was just dirty plugs?

2 comments

2 Comments

charles_henderson3d ago

Brake cleaner won't touch lead deposits, you need a bead blaster for that.

elliot_harris253d ago

Honestly, I've done the exact same thing on a Lycoming O-360 where I spent a whole weekend chasing a mag drop only to find out the plugs were just crustier than a week old biscuit. Ngl, it's humbling when you realize you could've fixed it in 15 minutes with a wire brush instead of tearing half the engine apart. Tbh, it's like when you can't find your keys for an hour and they were in your hand the whole time. Just makes you question every decision you've ever made as a mechanic.