There is a sound coming from the engine area that can best be described as a fog horn. This problem occurs mainly when the engine is cold and sometimes at operating temperature. I notice the volts gage dips, car runs rough and then recovers when this problem is occuring when at idle. There are no CEL issues however. When I step on the gas the sound disappears. There is a slight rough idle as well. Could this be a faulty IAC and/or EGR Valve or something else?
Thanks for the help!