My experience with amps is that the original solder was cold. Over time, the point gets brittle and cracks.

Then, 20 years later, you go crazy trying to find the cold solder point.

 

Main relay failure has been common in Honda cars since the 80s. They probably could use a well designed heat sink, but the issue does seem to present itself for many years so I don't think Honda ever tried to fix it

 

Many of these electronic failures in the late 1990s to mid-2000s were due to brittle RoHS-compliant solder (non-lead). Early Big Screen TV failures, especially. Companies were still adjusting their soldering robots' specs to the new solder.

 

Back when we still had to take "shop class" in middle school or high school it was emphasized that solder is NOT a mechanical connection, merely an electrical. Vibration will eventually fatigue solder connections.

Typical 90/10 solder won't melt under 500°F/275°C temperatures which are more likely caused loose connections or brittle solder rather than under-hood temps.

"Modern" surface mount circuit boards don't seem to have many mechanical connections and I doubt they're using 90/10 for these boards.

-- Chuck

 

I used what you guys recommended, hopefully that was a one time thing.

 

I noticed at one point you mention throttle position seems to impact behavior. I’ve had a similar issue reoccur on my AP1. The car felt fine until I went above maybe 90% throttle, then power would plummet. For me it was at the high end.

I wonder if you’ve tried to unplug and reseat the MAP and TPS connections (add some dielectric grease while you’re at it). Then, disconnect the battery to reset the ECU.

I don’t know which of those did it, or why, but that always sorted my issues.