This system uses a throttle cable to operate the butterfly. The throttle butterfly looks to open and close ok. The voltage from the potentiometer is within the spec listed on Bosch ESi at 0.3 - 1.0 v. I tried adjusting it and roadtesting but fault remains.
The customer has owned the car for a year. It has full service history and I can see no previous repair work that is relevant. I have a nagging feeling that all 1.4 Corollas of this design are the same as this car and there is no fault. I do not see many Toyotas due to there high reliability. The idle speed seems to be controlled ok and the fault is only aparent when driving. I would not be happy with it. Was partly hoping a AT member has experience of this specific vehicle to say I do have a fault or they are all a bit like that.