Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
She runs GREAT going down the road. However at idle, the engine surges for 15 seconds, then kind of evens out for 15 seconds, the goes back and forth between those 2 conditions. Sometimes it's not that exact and it may surge for 45 seconds.
While idling rough and surging the upstream 02 stays fixed rich. Fuel pressure regulator did not fix problem, and I'm totally lost as to what it could be now. Electronic Scope Compression check passed too. Help? Lol