Im not to sure if its the problem you got but this happened to my vr6 it ended up being the head gasket 2 of my cylinders were filling up with water even though there was no signs of it oil was fine still run idled normally no coloured smoke in the exhaust done compression test and all seemed ok baffled me to be honest but changed and fine now so if your mechaniclly minded and can wisk the head off quick to check or know someone that can them recomend changing it