We have a 2006 Mercury Monterey ie Freestar with 10,000 miles on it. About 2 weeks ago, it started to make this very strange UNPREDICTABLE surging or lurch while cruising. Happens every day, usually around 60 miles per hour. It is pronounced enough that the kids feel it in the second row. Dealer fixed the Advanced Trac sensor per the Ford service bulletin, said it was fixed and it did it again coming home from the dealer. Of course, the guy we bought it from thinks we were on ice, but the roads were perfectly dry. My brother is a Visteon engineer and he is convinced it is something with the transmission. The service people think we are absolutely nuts--of course, they did not drive the minivan when it was in for service.
Any help is greatly appreciated.

 

Keep pushing the issue since it's still under warranty. FORD does not like their Dealers to have "COME-BACKs" as it'smoney out of FORDs pocket for repairs that should have been done right the first time. The Dealer gets dinged for them. If you get no where with the Dealer, take it to a Dealer who will want to get your future business by listening to you to resolve your issue.They should always test drive a vehicle when there is a DRIVEABILITY issue involved. The Dealership that I use test drives before and after the repair. They will even have the Customer drive the vehicle with a mechanic riding SHOTGUN if the mechanic doesn't detect the Customers issue on a test drive. The OBDII computers are pretty good, but not that good. Surging/Lurching could be a selenoid, pump or clutch issue.