my noob guess. ECU are learning, but it seem like something or sensor give irregular reading so it try to counter it.
Scantool read any faults ?
See any engine that can use ur ECU as test to confirm its OK or really ecu kaput.
Don shoot me, i'm learning too. :hmmmm:
not a crazy suggestion, some ECU's have 'learning' abilities, the ECU in the 2001 Audi TT which was the last car I owned in the UK before moving to Asia 'Learned', you could notice a slight difference if you disconnected and reconnected the battery, miss that car
In this case I don't think the tick over at cold would be so bad however, also as you suggested they already tried my ECU on another car withe same engine and no other issues, and the rough running at idle when cold issue was duplicated when my ECU was plugged in. They did use a scan tool to look for error's, and none came up, then they sent out for a ECU specialist who hooked the ECU to his notebook and said there was an issue.
Not sure of the exact issue as they were talking in Thai, and my Thai language skills are not good enough to understand exactly what he said.
Hopefully the replacement ECU my friend found will work, will keep the other one and try and get it fixed if they don't give me money off.
thanks for all the support so far!