In Reply to: M 40 Engine posted by ken on March 26, 1999 at 06:01:59:
: I've a 518i E34 1991 with an M40 Engine. It's an European model and there is a lot of problem like clicking sound from the engine when driving uphill.
: It has a problem when trying to start the engine when it cold as it takes time to idle itself. I have already changed the idle stabiliser valve but nothing seems to have changed and there is also a problem when using electrical devices like the front lamp, electric windows etc... as the idle speed tends to go down.
: I would like to know which are the best spark plugs to use for this engine
: Is there anybody who could help me.
Hum, You have indeed a very rare model for a 5-series, most of us are used to a 6-cyl beginning at the 520i wich is basicly the same engine as a 525i (M50).
The clicking sound, maybe this is predetonation due to bad fuel, too low in octane. SO the ticking-clicking sound could be your valves. Try to fill it up with a better fuel, in Europe (where I am also, Belgium) you can get Eurosuper at 95-96 octane or Superplus at 98 octane.
It could also be carbon deposit on the valves, try when filling up to use a injection and valve cleaner, do this twice.
Idling-problem: may be caused by a vacuum leak on the air-intake or may be linked to the dirt on the valves and injectors, who knows.
Electrical problem: I presume this is the voltage regulator, cheap and easy-fix.
If you would like to know, your engine is chain-driven and thus has no belt to replace.
Is this a pre-owned BMW? Did you bought it recently?