My 1989 260e used to do the exact same thing... unfortuanly I never realy did figure out what the deal was with it but it did often have an O2 sensor fault set by the ECU (even though I replaced it).

I guess this post is not much help beyond... "Hey.. I've had this problem too with a 260E". It never really got worse though.... I just had to think twice about jumping out into any traffic....

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