JasonInMontana

Michael, My Subie had a knocking sound that sounds much like what you are describing. It turned out to be bad struts in the rear. the knocking sound occurs as the shafts shift around inside the cylinders.

I had issues with my '98s heated seats initially. Pulled the seats out, pulled the covers off, the element was burned in two in the forward center part of the seat. Tried soldering a bridge wire across it, did not hold up for long. Ultimate solution was to use a crimp-style connector on each end of the wire to bridge the gap. No problems since then.

After reading the entire thread, I would say most likely cause is head gasket. The '98 2.5's were notorious for blowing head gaskets. They could blow at any time from recently replaced to over 75K miles. Never was very predictable on the "when" part. The most reliable solution I've found anywhere is to replace the entire 2.5 engine with a 2.2. Only real side effect is the check engine light stays on because the 2.2 has no EGR system.

Have you cleared the codes and then checked that they re-set? Is it getting fuel? Can you hear the fuel pump power up when you turn the key on? Is the fuel system pressurizing properly? And like the others said, check the timing belt. Make sure to do all of the zero-cost checks before throwing money at hit-or-miss possibilities.

Had a similar problem recently with mine here in Montana. With the onset of Winter, I started getting misfire on 2 & 4, plus a knock sensor code. Replaced the knock sensor with one from a junkyard, code went away but problems persisted. Replaced the plug wires and everything has been fine since then. NOTE: there was no physical evidence that the plug wires were failing, they looked good on visual inspection. Don't trust your eyes when it comes to bad wires.

Does the 2.2 swapped in have an EGR valve or is your check engine light perpetually on? Just curious, because if no CEL and no EGR, would like to know how this was achieved.