Power Comes and goes between RPM 1000 - 2000

Hi guys,

V6 ( 3.0L) automatic. Mileage: 127000. The car starts and idles well. However, when I drive slowly with the RPM in the range of 1000 to 2000, the engine power comes and goes even though I keep the accelerator peddle pressed at a constant. When this occurs, I can see the RPM meter needle swing up and down fractionally. Although the engine is quiet I can hear the engine power coming and going and also feel it since the car rocks forward on the power surge and slows when the power goes off again. The frequency of this is I guess, approximately two times each second.

However, when the car is stationary this does not happened even if I bring the RPM to that level. (The engine is very smooth then). And when I go over the 2000 RPM and cruise on highways the drive is smooth and there is no hint of this.

I recently did a major service where the fuel filter, air filter, gear oil, gear oil filter and the timing belt were replaced, hoping that it will solve this issue. In addition, I asked the mechanic to check why this happens. However, they appear to be stumped after doing a full check of the car’s emissions and all other things ( I’m not too familiar with what they checked exactly) and told me that the car came out clean in all the tests they did. Their final advice is to drive until something of “substance” comes that can be detected by them. This does not sound as good advice to me since it may land me in even a bigger problem later.

I would really appreciate if you could point me to what you feel needs to be done in order to solve this problem. Thanks a lot!