i may be able to shed some light on thisfor ya'll ihada88 regalcoupe thatdid the same thing rpmswoulddipwaylowandbackto750 or sothen backdownor wouldrevup to 1500andgo back to 750-800rpm when i had the cari wastold to pull the main fusesunder the hood andleave themoutfor amin or so then put thembackin anddrive the car25 miles to re set the ecm seemed to word as only had to do it once and car ran fine after that keepin mindthe regal had 160,000plus miles on it to but other then the weird idle ran greatotherwise returning 23-27 mpg good luck and hope this helpsya'll some
