"Don- which motor is this? Can
"Don- which motor is this? Can you post a couple of photos? Have you run it since the power loss after lunch? If not, it could have been a heat-soak situation and the ECM acted like the motor had overheated. If you're in a hot, dry area, this is definitely possible. Make sure the tech cleared the codes and checked for overheats. Overheats don't clear as easily as other codes. If it didn't go over 2000 RPM, I would almost bet that this is the case.
charli- the ECM will add fuel if it thinks it's cold or did you mean reduce the fuel from "cold start" to normal operating temperature?. The timing would be unaffected by a bad ECT unless the knock sensor sends a signal.
Don- speaking of knock sensors, look on the side of the motor with the starter for a blue wire with a black plug, dangling in the air. That needs to be plugged into the large, gold colored device mounted where a block plug would go (just above the oil pan). If it's shorted to ground, it'll also cause problems. This would show up as a 43 or 44 code.
If the motor is run out of the water, look for cooling water flow and make sure the exhaust isn't plugged. There may be a flapper in the exhaust and if this melts, it won't move out of the way when the motor runs and can cause problems.
Since it's kind of rough, it sounds more like a shorted ECT wire/bad sensor, causing the ECM to see an overheat and go into RPM reduction, but that should have thrown a code. At normal operating temperature, the coolant temperature sensor should measure about 1.5-2.0 Volts dc, and this translates to 332 Ohms @ 80°C/176°F and 667 Ohms @ 60°C/140°F. This is measured on the two wire sensor (yellow/black wires), located on the head between #3 and #5 cylinders (usually). I have seen it in the intake manifold, but its location depends on the motor."