The “Check Engine” light in our 2002 Subaru Legacy came on a while back. The symptoms were a sputtering, jumpy engine only on cold or wet mornings. The symptoms went away after the car had been driven for a few minutes. An OBD check revealed that the issue was a cylinder misfire. My mechanic said that it could either be bad spark plugs or bad wires going to the spark plugs. It would have cost several hundred dollars to have him do the replacement, so we put it off for a while. The spark plugs are the cheaper of the two parts to replace, so eventually, I decided that I’d like to try replacing them myself to see if it fixed the problem. I have the Haynes manual for our Legacy, which details the procedure, so I felt like it was pretty do-able. In additional, I also found this video that details the entire process on the exact same engine as we have.
The process went pretty smoothly overall. I had to remove some unrelated parts from under the hood in order to get access to the plugs, which are mounted on the sides of the engine. The air intake had to come off completely, and the wiper fluid reservoir had to be disconnected and moved out of the way. Other than that, it was pretty straightforward.
It was a bit nerve-racking as I prepared to turn the engine on for the first time after the replacement. I wondered what would happen if I hadn’t installed things quite right. But I had nothing to worry about, as the engine started up just fine. I took a test drive and everything ran smoothly. That was a week ago, and the car has been running great ever since! No bad starts, and the check engine light turned itself off. The cost for the spark plugs was only $10, and I also had to buy a longer extender for my ratcheting wrench so that it could reach far enough to grab the spark plugs, but other than that it was pretty cheap and a good investment of my time.
You can see some more pics from the procedure in the gallery.