Stalls when cold

Q For about a year, my grandson has had a problem with his 1995 Mini Cooper 1.3i single-point injection. The engine will start, but will stall when cold without throttle input; when the engine is warm, the idle will be very high.

Initially, the revs kept increasing and reached somewhere around 3500rpm. On the day that happened, he added Redex to the fuel tank and the problem went away. At this point we thought it was a fuelling issue or a stuck injector, but the engine wasn’t stalling. When the problem returned, the idle went up and down with a difference in speed of around 500rpm, then it went to a high idle, stalling when cold. Since then I have changed the vacuum lines – this seemed to bring the idle down, but it’s still too high – along with the HT leads, distributor cap and a few other components.

After getting a diagnostic scanner that would work with the Mini – it has the MEMS 1.6 ECU with a three-pin connector – I’ve found that it won’t connect. I am not sure if this is just a short loom problem or if the ECU is faulty and causing the other problems as well. R Wilks A As the vehicle hadn’t been driven for a short while before the problem developed, it may be related to a number of fuel injection issues, especially if the fuel system dried out while the vehicle was laid up. The most likely culprit is the idle speed stepper motor, which has possibly become sticky or failed due to inactivity.

On the single-point injection units, the stepper motor is directly connected to the throttle, unlike the MPI unit which uses an idle air control valve. The stepper motor has a series of windings, and one or more may have failed or have a dry solder joint internally.

A new stepper motor is available from minispares.com for £90, which should hopefully resolve the issue.