BMW 318IS M44 surging idle

[frankb]

Recently replaced spark plugs & manifold gaskets on 1997 318is with M44 engine. Car starts easily and idles normally untill it warms up then the idle surges between 1000 to 1500 rpm's. Any ideas?

[Jeron]

Intake manifold gaskets? Are you sure you didn't forget to replace something?

I would check for intake leaks. Get a spray designed to find vacuum leaks and use it discover and pinpoint leaks.

[frankb]

Initially forgot the coolant hose to manifold spacer and had coolant leak. As far as I can remember there are only two vacume lines, both at the front of the manifold, and they are both connected.
Why surge only after warming up for four to five minutes?

[David Bevan]

The mixture on cold start is enriched to compensate for fuel condensation, when warmed up the fueling reduces to the normal map, which will be slightly leaner under these conditions the extra unmonitored air from a vacuum leak will cause hunting/surging. Some of the pipes may be a bit ripe and have cracks in usually under the inlet manifold. these wouldn't show up until you have worked on the engine and disturbed them.

[frankb]

Problem may come from Bosch idle control valve. Is there any way to check?