There is no Check Engine Light warning about this, and it only happens in a limited range between 1500 to 2000 RPM. But unfortunately the narrow range happens to be a very commonly used range in low-speed city driving situations. So without a CEL warning, it would seem to me that whatever is causing this is not serious enough to trigger a warning from the engine computer. What could possibly be causing this? Transmission slip, intake manifold vacuum leak, dirty throttle body, plugs or leads, etc.?
Car: 2008 Tribeca, 3.6L, auto.
Yousuf Khan