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Have a minor issue that is annoying rather than "end of the world". 308k motor, but still healthy apart from noisy lifters, farts and coughs a bit when cold, at low revs. Partic on initial opening of throttle. Once warm, seems fine.

Not sure if it started then but I noticed first after washing motor = water somewhere? This was many months ago but problem persists.

Have put new plugs and leads on to no avail.

Car has cold air induction and extractors

Coilpack, extractors, o2 sensor, early dementure? Any ideas?

Clean your throttle body, cold start valve, and isc valve.
Will do wonders

It'll probably settle down all by itself over the next 100k. Congrats on the 308k you've got already.

I'd check ISC and cold start first too.

If the problem began after a wash then you could check for corrosion inside the holes on the coilpacks where the high tension leads plug in. I assume you've already checked for water and crud in any other plugs and connectors that could have got wet. CAS connector, engine loom connector at the back of the inlet manifold, AFM plug and TPS plug would be the ones I'd focus on.

Also one of the coolant temp sensors at back of head on the NA6 provides a signal to the ECU. When the sensor goes, which is common, you get poor cold idle as the ECU doesn't know it's a cold start.