Expert: Josh Fields - 8/19/2006

Question
Hey Josh,

I've got an 1986 325e automatic. When I start the car the engine
immediately jumps up to rpms, stays there for 3 seconds or so,
then drops down to rpms(its more normal running speed) and
then rises again, and drops again over and over like it is cycling
over humps...When engaged in the drive gear, it drives fine, but I
can still feel it pull forward a little and then drop to a lower gear
(I can even hear clack and jerk a bit) and repeat itself as it does
in the nuetral gear. Unless I am depressing the accelerater pedal
this is the car's behaviour.  A friend of mine who works on cars
told me that it could be the mass airflow sensor, but I thought it
would be the fuel intake sensor. Your thoughts please!!!!

Thankfully,
Victor

Answer
Victor,
 This is a common problem, and it doesn't have a common cure.  There are a couple different reasons for this to happen.
 The Air Flow Meter could be one of them.  I dont know what a fuel intake sensor is, but I know the BMW doesn't have one (at least the ones I've worked on).  The Idle control valve could be dirty and a good cleaning might fix it.  There are also some sensors on the thermostat housing that will affect how the engine runs.

 Good Luck,
 Josh