2003 330Ci: Strange vibration after warm start

[autobahn71]

My 2003 330Ci Cabrio runs very well and it was recently serviced by BMW at 156'000 Km, but it has started doing something very strange. If I start it from cold, no problem whatsoever. But if I restart it after leaving it parked for less than 1 hour, with the engine still warm, after a few seconds the whole body, steering wheel, gear knob will start vibrating very strongly. It's a nasty, powerful vibration which only lasts 20 seconds or so. It seems to be independent from engine revs, even if I rev the engine very high the vibration continues just the same. The strangest thing is that it disappears by itself after 20 seconds, and the car is perfectly fine afterwards.

I have found many threads on COLD start issues, but nothing on WARM restart issues. If anyone has any ideas please let me know, because I live in Switzerland and letting a mechanic loose on a mystery fault search will cost me 150 bucks per hour! I'd rather go to the mechanic with a solution in hand.

Could it be the VANOS seals? If so, why only on warm restart? Or could it be the engine mounts, which are worn out and give way when the engine is hot, but then why do they sort themselves out after 20 seconds?

Any help is welcome...

[MarcoZandrini]

The first step in diagnosing a problem is to scan the engine computer (DME in BMWspeak) and the automatic transmission computer (EGS) if the car has an auto transmission. The service engine soon (SES) light is on only when there’s an emissions related code present.

Is the fuel pump original? When was the fuel filter last changed? It sounds like you’re issue is fuel related.

[johnjmurray]

I agree with Marco. You should have that filter changed. Don't rule-out your motor mounts, however. Their break-down can be subtle but this throws off the whole driveline.