I have a 2007 Dodge Durango with a 5.7 hemi we just bought the vehicle everything was going great vehicle suddenly started fluctuating in idle while going down the road feels like the transmission is shifting up and down I don't believe it is. It is now also surging at idle any thoughts or ideas???? the gas cap light did come on as well but only for a short time no other dummy lights or indicators. the compass readout says system is okay....... Okay go