With each consecutive maintenance procedure, I become ever more impressed with the engineering on these cars. I have changed THOUSANDS of sparkplugs on hundreds of engines, but given the apparently difficulty of this on a Gen 2 Prius, they were shockingly easy to change. Despite the records indicating plug change about 80k ago, our car developed a VERY intermittent misfire with flashing CEL (engine shaped light). Research led to the likely cause of misfire induced by sparkplug(s). I hold shops in dim light and expected to find el-cheapo Cu plugs that were wrong for this vehicle, but I was proven wrong; the correct NGKs were used. In any event, there was moisture in two of the four plug wells and rust in #1, easily explaining our symptoms. Given there was no DTC logged, I checked FIRST, I am confident that the defect was caught in the very beginning stages.
DIY is as easy on a Subaru as ANY vehicle I have ever seen, but the logical lay-out and engineering of the Toyota is hard to beat!
I DIY oil changes on all my vehicles over the years and our Outback is, by far, the easiest and most thought out of all of them: ride height is high enough to not need ramps or jack stands to get underneath and the oil filter mounted up top, up front, and upside down so it drains back into the engine.
My '98 Outback with the 2.5L is a very hard spark plug change. Yep, the Prius is a snap for many routine tasks. Flushing brake fluid and changing engine coolant are among the exceptions, though with the MiniVCI they're not so bad.
Hopefully you applied some caulk or a new rubberized weatherstriping (Shop M-D Building Products 0.75-in x 10-ft Black Sponge Rubber Window Weatherstrip at Lowes.com) to replace the factory seal in the middle of the cowl. Post 1 has images of the original seal; Hood cowl engine compartment water seal questions | PriusChat Yours are probably well worn or gone. This center cowl seal is a common problem on Gen2s.
