RPM'S Surging

[Nielsen]

I took my 2003 Hummer to the dealer service department today to have the engine looked at. I am experiencing surging or fluctuating rpm's while maintaining a constant speed, in the 40 to 60 mph range. They have not diagnosed the problem yet. RPM surge is about 50,.... small, but significant enough to feel. Even passengers have asked what,s wrong. They can feel the pulsating also.

Has anyone else experienced this, or have an idea??????

Thanks