Family friend has a ‘99 Deville. About a month ago he decided to wash his engine bay. The following day he suddenly had misfires on multiple cylinders.

He’s in his 60's and while he has always been a car guy the newfangled computers, sensors, and associated technology are scary inconceivable stuff to him. My obd2 scanner was like the most amazing thing he had ever witnessed.

He had initially refused to believe soaking down the engine bay had anything to do with it. We were discussing coils and after verifying the misfires were happening on cylinders using different coils I explained how it was statistically impossible for multiple coils to crap out at the exact same time. I did mentioned water intrusion could have played a role in precipitating multiple pack failures but they were well sealed and it would be highly unlikely. He didn’t believe me and went and bought 2 new coil packs and asked me to replace them. I did, and it kept right on missing.

Tried for weeks to get him to allow me to pull the spark plugs to examine them. He was absolutely convinced that I would be unable to access the rear 4 cylinders.

Well, I finally convinced him to let me have a go. The plug wells were full of water sand and oil. Cleaned the wells, pulled the plugs and they were original to the car. Super filthy and oxidized on the top half, and fouled as hell on the bottom half.

Hit the plugs up with brake and electric cleaner and a wire brush. Blasted the plug boots with cleaner, reassembled, and she purrs like a kitten.

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Now I’ve gotta convince him to buy new plugs and wires and let me install them. The hard part is over though, and it was much easier than even I expected.

Mended, and I didn’t even need to use Jezzas hammer of fixology.