Recenlty purchased 2007 Ford Taurus, 31,000 miles. I have noticed that while sitting at light in traffic, the rpm gauge jumps between 600-800 rpm. I have no heating/air controls on, wipers are off, the only thing running is the vehicle. I am aware that different compressors and pumps do run while the vehicle is running. I can feel the vehicle get bogged down when the guage reaches the lower RPM. Is this normal? I took it to the dealer and they said that it was because I had my heater on. I didn't have time to argue so I dismissed it, thinking they had looked at it. It was a cold morning ,and the switch hadn't moved. I was told that it could be bad gas, used injector cleaner, higher grade for a month...nothing. Any ideas would be great, preferably within 5,000 mile warranty...
Thanks in advance,
JM