Lumpy Idle and Servo Issue e36 M3 Coupe

[mjenks]

I have a 1997 M3 evo.

Recently it has developed two problems which appear to be related:

1 - very lumpy idle and running even when warm
2 - intermitent servo failure (normally when it has just started).

The diagnostics show a vanos issue.

I have had the solenoid to the vanos disconnected and this makes no difference. My mechanic believes we have a vacuum leak which is drawing air - this makes a lot of sense.

The pipe to the servo (brake booster) has been disconnected and this too makes no difference. The inlet manifold has been off three times and two pipes replaced still no cure.

We have tried squirting fuel into various areas of the engine to see if the leak sucks in the fuel and stops the poor running - no joy here too.

Has anybody else ever had this type of problem and if so how was it fixed - any suggestions as to other tests we can carry out.

Thanks

[m3pilot]

When i took the plenium chamber off of my evo the ait intake between the throttle body and the plenium chamber where the throttle cable bolt on had broken which caused a small vacume leak.

Also on the E30 the gasket between the throttle body and head can leak causing lumby idle, not sure if this also effects the E36 but it could do. Think they were around £200 from BMW for the E30.