In Reply to: 1991 735i rough idle and lack of throttle response posted by Nick Little on October 08, 2001 at 21:43:58:
1) fresh fuel of a good grade?
2) tried running some injector cleaner through - usually not to get clean the injectors, just to flush out any water stuck in them
3) checked the air cleaner?
4) checked the battery voltage WHILE IDLING? The electronics need a good constant voltage at idle and the alternator isn't always keeping the battery voltage up.
5) cleaned the ICV (idle control valve) with some carb cleaner
Other ideas would be much the same as checking the "rough idle diagnosis" page on the bmwe34.net - Brunos' site covers the 535 very well, and it's the same engine...
Hesitation off idle can also be the extension of the bad idle - I'd personally get that in order first then progress. The idea with the TPS isn't that strange either - there is one, obviously - but it's setting should be done in conjunction with the setting of the throttle-plate clearances.
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!