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Help Requested - getting desperate!

747 views 0 replies 1 participant last post by  markus 
#1 ·
I have 1989 E34 5 Series that suffers sporadic periods of severely running rough. It can occur both when idling or driving/when warm or cold. it seems to suddenly develop an overly rich fuel flow resulting in black smoke from the exhaust and very rough running. the problem can disappear as quickly as it arrives.

It has services, throttle body cleans and injector services by qualified (non BMW) mechanics without solving the problem. Most recently a couple of the vacuum houses have been replaced.

It was recently noticed that there appears to have been a piece broken off the non-return valve. (see the 'nub' indicated by yellow arrows in attached pics). The 'nub' has an uneven surface (not machine moulded) suggesting something is broken/missing.

Should there be a valve there? Or a small hose? If so where does it go?

There is nothing indicated on the parts manual to indicate another hose or control should be there.

All i know is that 'nub' allows air to be drawn into the system. Placing your thumb over the whole affects the idle speed and smoothness of idle.

Anybody have any ideas?

I'd really be very grateful for any help! Thanks.

Markus
 

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