Do you have the T16 Rover engine?
Ive found that the TPS (Throttle position sensor) and idle control stepper motor do get rather confused
It does on our year 2000 rover t16 car and Ive found that if you put your foot down a little on the accelerator than turn the starter key she fires up first time.
There is a MEMS piece of software you can run on your phone as an app and have a micro usb to rover mems cable under dash connector to see what the engine 'sees' also shows if you have faulty sensors.
Morgans 1934 MX, 1947 Series 1, 1956 +4 TR4, 2000 +4 T16
Triumph Herald 1969 13/60
Morris 1970
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