In 2010 I had Caterham Works upgrade my Supersport Rover K Series 1.6L with the Supersport Eng Kit (stock SS03K). This involved amongst other things changing the Engine Control Unit to the EU3 version and adding a yellow LED in the tacho. Ever since I've had an occasional problem at startup which exhibits as:
1. Yellow LED stays ON whereas normally it goes OFF once the engine is running
2. The engine stalls if you let the engine idle. To keep the engine running you need to keep your foot on the accelerator
To resolve the problem I just need to getup speed, take my foot off the accelerator, let the engine stall and then do a bump start. The yellow LED goes out and the engine returns to normal.
I've noticed over the years that the problem seems to be associated with low battery charge. Currently my battery is on its last legs so it happens 50% of the time. It almost never happens when the battery is fully charged which is why I've not addressed the issue before now.
I suspect that the ECU does some diagnostics at startup which includes checking the battery level and if lower than a certain voltage the code enters 'limp home mode' which results in the yellow LED staying ON. If my suspicions are correct then a fix would require either blowing the EEPROM with a new version of the code, or replacing the ECU entirely.
Has anyone encountered similar problems? What was the fix?
In 1980s I worked in a team responsible for programming the ECU in Ford cars so know a bit about 'limp home mode'