I have a 1991 735i which has been running fine up until recently. Of late there have been problems with engine idle and lack of throttle response. The symptoms are broadly as follows...
(1) Stopping at lights the engine sometimes stutters/surges. If in drive with no brake applied the car will jump forward in little hops. Changing to neutral has no effect. As I brake to stop I can feel the engine idling quite low, then when I stop it feels like it's alternating between idling too low and normal idle. If I put my foot right down to the kickdown on the accelerator it will come right suddenly after a couple of seconds.
(2) Driving along open road/motorway (typically) I take my foot off the accelerator. The engine then idles and often I can feel the auto transmission "brake" depending on my speed at the time. When I put my foot back on the throttle sometimes nothing happens (no revs/power at all - just dead) unless I push right through to the kickdown position on the pedal. At that point it takes a couple of seconds to respond - then it very suddenly kicks into life and is fine until it happens again.
I've only had the vehicle for the last 10 months, and it has been serviced twice in that time. Service history prior to that is good, but I don't really know if there were any other issues in its past...
I've had similar problems with another vehicle, which turned out to be an idle position sensor issue. This wouldn't explain the throttle behaviour though, would it?
Cheers and thanks for any response!