The problem occurs on M52TU engine cars, 3 & 5 series 6-cylinder 1999-2000. It presents when the car is cold, ~ < 55° Fahrenheit, usually in the morning. The problem begins at the end of the warm-up period (elevated idle rpm). Thus the colder the car, the more delay after startup before the problem manifests. At the end of the warm-up period the engine begins a series of stall encounters. The engine rpm’s drop significantly, the engine shudders, and then the engine rpm’s recover. This engine jolt lasts ~1 second. It is followed by a steady idle for ~7 seconds. The cycle then repeats. This continues for ~4.25 minutes. The 7 second idle interval can also be shorter, even to a ~1 second interval. With some cars the engine will actually stall on one of the engine jolts. If the car is driven before/during the episode, the problem seems to be suppressed, unless the car shortly comes to an idle state where the problem reappears. If the hood is opened, a gear/chain like chatter can be heard during the stall encounters. The idle control valve can sometimes also be heard clunk open.
The M54 and M56 engines share the same vanos as the M52TU engine, but don’t exhibit the “vanos problem”.
Je suis désolé pour ceux qui rencontrent ce soucis et qui pensaient le remède simple et pas cher mais à l'heure actuelle, seul le changement du Vanos complet est possible, les joints de segmentation ne se vendant pas séparement.We suspect the M52TU cold engine “vanos problem” is related to the M52TU DME. The DME is likely not receiving the anticipated indication from the camshaft position sensor, and reacting in a way that causes the engine to almost stall. The DME could be over opening the ICV causing the engine to almost stall. This can also explain the ICV clunk that is sometimes heard during the engine attempted stall. We expect that the M54 and M56 DMEs function differently and thus do not instigate the cold engine stalls.
Upon further inspection of the vanos piston seals, we’ve found that each seal is not one component but a set of two rings. There is an outer Teflon seal ring, and an inner (supporting) elastomer o-ring. We believe it is the inner elastomer o-ring that wears and shrinks, causing the outer Teflon seal ring to retract, and thus creating the leak condition.
mais toujours sur 6enligne !!!! 
C'est à dire marcorel ? chronometre pour quoi faire?marcorel a écrit :Salut,
Très interessant ton post allroadusa
Ceux qui ont le problème n'ont plus qu'à se munir d'un chronomètre et vérifier tout ça ;)
Et parmi ceux là, qui a un vanos neuf ?
@+
Dans l'article, il est écrit que le phénomène n'intervient que sous les 55F soit 12 degrés également ! Pas de doute sur les symptômes donc.SCLAUX a écrit :Car moi qui ait le probleme ,, ça n'arrive qu'à température exterieur inférieure a 12 degrés en gros.
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