Hi Dave!
My husband & I purchased a 2006 Mercury Mountaineer V8 AWD Premier with 3rd row seating & tow package just a few months ago in June 2016. When we purchased her, she had just over 100,000 mi on it, literally. About 1 month after our cash sale purchase date, I began noticing a few strange behaviors, (that all of which, including the one of topic in particular, are conclusively way-to-common malfunctions for beyond too many used Ford Explorer Eddie Bauer Eds.-by pattern, appx. model years between 2002-2010, Ford Explorer LX/EX(whatever the top edition is under the Bauer editions)-2006-2010, & Mercury Mountaineer Premiers-2006-2010. A decent majority of posts like yours started around 2009/with avg. vehicle mileage at occurance was just over the 60,000 mi range. In my case, it started with my suv starting to slightly buck("shimmying" as now designated for us-lol), at any point within or between gears, with acceleration, happening most frequently when driving on the highway. It does happen when driving at any speed on any road, but is amplified on the highways due to insane traffic causing to have to switch lanes and therefore adjust stored for each, etc.-but also note that even the world's steadiest driving foot/smoothest driver could not prevent it from constantly occurring. The bucking also sometimes causes jerking so bad that I & many others have all shared an immediately reaction to assuming we had been rear-ended, that it is going to end up snapping the front axel/control arms/balljoints at some point, & having caused widespread panick when simply trying to merge at normal range with highway traffic when our vehicles failed to build up enough speed stepping on the gas pedal, causing three lanes of traffic to slam on their brakes & have to go around you. Many of us have realized we can almost somewhat "override" the bucking in a way by giving it a bit more gas just as you feel the vehicle siezing to buck, as well as by letting off the gas when the auto trans about to switch gears. Today, your story above had happened to me almost EXACTLY the same. (Outdoor temp @ the time was 55 degrees so def not heat-induced.) I had been in a parking lot, in "P" for appx 10-15 mins before ferrying ready to pull out of where I was visiting. Had the heat on & was fine pulling out slowly of the complex. As I turned left onto the main strip and tried to increase speed, I almost immediately heard the same, very loud, (but a bit lower-pitched tone) roaring coming from under the hood. I had described it to my husband via phone as my involuntary reaction had assured was sounding like a city public transportation bus starting to go from a stop light. I had immediately panned the mirrors as soon as I heard it as it was so loud I thought an 18-wheeler/ city bus was riding my behind THAT close. I also then moved on to the premise of overheating and also saw my temp gauge was completely normal and not at all moving/twitching or anything, (no smoke, no smell). Checked to make sure I didn't accidentally shut off "O/D", quickly moving on to radiator/blower motor problems that maybe brewing caused by my pretty high heat blowing. So I shut the heat off, & just the same as you, it did not affect anything and the noise persisted. So I pulled over, shut the car off for 30 secs, turned it back on and now an hr & a 1/2 later, haven't heard it since. I know mine & others previously-mentioned malfunctions are (no doubt in made my mind) relayed to this "shimmying" issue. No one is finding answers from multiple mechanics, techs & certified Ford techs/dealership repair all having investigated, nor getting is Ford even acknowledging the way-too-many people reporting these issues & extreme consumer demand to recall. It's not the transmission, it's not the torque converter, its not gas emmitance system issues, its not spark plugs, its not engine/gasket head issues,v its not radiotor/coolant/blower motor issues, its not an ABS issue, & the only hint our vehicles provide us to assess the issue, which is the Powertrain Indicator Light coming on for only a breif time, ends up not throwing any code at all when plugged in asap, and reads as if nothing at all happened, showing no indicator lights came on at all. And this is where we hit the brick wall deadend to getting absolutely nowhere & no assistance, not even the very least, recognition/acknowledgement of this problem leaving so many of us with no $ to purchase a different vehicle most having just purchased 2nd-hand; no indication of any sort to direct even the best mechanics at least in some sort of idea path toward solution AT ALL; & lastly/worst of atl beaten suggestions to our inquiry reports already tirelessly explored & doubled-over; silence without a hint of admittance to recognize a very blatantly obvious ongoing widespread consumer-reported problem that should have already been swiftly recalled a long time ago as even the most non-mechanical individual can recognize sizeable-enouh evidence back in 2009! Please Ford: don't let anyone get hurt before coming to a simple conclusion.
