My 93 240 has an issue on low pressure days. Sometimes she doesn't like to start up, but its mostly that engine stumbles and dies on acceleration. I can rev the engine in park and nuetral and there is no stumble, only when I engage the transmission. Sometimes I lean toward lack of fuel, but am leaning more and more toward vacuum leak. I know there are some vacuum issues because the heater flap/door never totally closes. Is there a relation. Fuel pressure regulator and Throttle Position Sensor changed summer before last.

This situation ussually only occurs in the morning on damp, humid days. Does not come about after car has been sitting all day at work.

Help greatly appreciated.
--
Loose Moose