"Pop" sound under acceleration

[ric220]

Happy NY all!
When accelerating hardish from low speeds I often get a loud "Pop" from under the bonnet on my E280 W124; the car seems to loose power for a split second then accelerates fine. Any ideas? There is a tickover problem which my local Merc specialist hasn't been able to diagnose as yet (revs bounce when stationary 400 - 100RPM, revs fail to drop when easing off accelerator at lowish speeds etc) - could this be related?
Would appreciate any pointers.

 

[Ultymate]

Sounds like you may have an air leak on the induction side of your engine ie vacuum pipes inlet gasket(s) etc

 

[ric220]

Would that account for the poor tickover etc as well? What test would a decent garage do to identify where the leak might be?
Thanks.

 

[Ultymate]

Yes it would account for all your symptoms, I don't think there's specific tests just a good mechanic with a tenacious approach is needed:???: