BMW won't help me so it's DIY time
Car has reached 200000km without any probs except the so much discussed eratic idle problem. I want to fix that. BMW dealership here don't want to spend their precious time looking an old M40 engine to fix this problem (as it may have multiple sources) so I thought of starting doing things myself.
What's the first thing to check?
I've replaced the engine gaskets, idle valve/ relay, fuel pump (was defective), fuel lines, fuel filter, oil filter, air filter (K&N), spark plugs.
I'm thinking of cleaning the air flow sensor is that a good idea as one step further?