[Elwood]

Okay, I bought the 1985 final edition Cadillac service manual and have read it cover to cover, run all the diagnostics and still have the stumble and surge drivability issue with no failures detected through diagnostics other than one occurrence of a soft error #23 which seems to have registered during my normal commute. The “mystery “ information center indicators I documented earlier were due to the engine dying immediately after hot start, which has now occurred 3 or 4 times (had the radio too loud and miss-diagnosed the first instance). The surge condition seems more engine RPM than throttle position related, i.e. if cruising at 30-40MPH and experiencing “significant” surge/pulse/hunt conditions along with extremely erratic “fuel information” data a change to “drive” (3rd gear) from “overdrive” with no adjustment in throttle position immediately cures the symptoms. Similar response is observed at 15-25MPH cruise in “drive” when the transmission is shifted to L2 (2nd gear). The car still runs great in all other conditions and is still getting “typical” fuel economy (~19 city, ~23 highway). One other significant observation is that upon release of throttle to coast down from nearly any cruise speed, and even if above conditions are occurring, the fuel information display stabilizes at “reasonable values” for 5-8 seconds and then reverts to rapidly changing blank/numeric/alphanumeric values and random lighting of the “Range” mode indicator. The book doesn’t seem to have a cure for these symptoms so I’m all ears.