Hi, I've had an intermittent idle problem that's getting worse. Car starts fine, but after it's warmed up, it starts to rev too high in idle. This can sometimes be controlled by pumping brake hard (brings it down to normal level) though not always. Sometimes revs up to 2500 without touching the accelerator - other times it may stall in neutral. Some days it runs fine. Had the idle valve control cleaned, which seemed to help for a while, then replaced. But replacement valve hasn't solved problem. Took to BMW approved garage. They say that engine control unit is fried due to water getting in (design flaw of these earlier models - it has been raining a lot!) and will cost over £1000 to replace - but they can't guarantee this will fix the problem.
1. Does ECU sound like it's the problem here?
2. Is that a reasonable quote for replacing ECU?
Any advice appreciated. Apologies if I've not phrased this well - I'm not mechanical and new to the forum.