Loss of power after overheat
I overheated to the point of engine stall after a bad coolant leak. After replacing lost fluid and field patching the leak engine ran OK and I've put a few thousand miles on it since. But I've noticed a significant loss of power (and it sounds like I have a mild misfire at full throttle as well), and 20% lower gas mileage. Noticed engine is running a little rich (blackish tailpipe as opposed to dark brown before), but plugs are clean. No indication of blow-by (oil clean, no visible smoke from tailpipe). No trouble codes. No fluid losses (beyond what deteriorating gaskets have been causing over the last ten years).
FYI 373,000 on original engine w/ no replacements other than typical maintenance (e.g. TPS, O2, crankshaft position sensors, plugs/wires/cap/rotor in the last two years).
Any idea what the problem might be?
1988 Jeep Comanche
4L, 4x4 5 speed manual