2002 SES surging when accelerating

My wife's car is a 2002 Taurus SES "Sport", with the 24V Duratec and console mounted shifter.

Here is the problem: When travelling at speeds of, oh say, 40 - 60 mph, shifter in OD, if you apply the gas pedal enough to get over a mild grade, the car starts to surge, or pulse. If you step a little harder on the gas, enough to cause the tranny to kick down, the surging goes away. If you drive on secondary roads with the shifter in D as opposed to OD, the problem never happens.

This is a fairly recent development (last 2-3 weeks). The car has about 105,000 miles on it. I'm sorry to say that it has only one Tranny service done to it in it's life (my bad). It has had regular oil changes, brakes, tires, etc. I generally don't drive it so out of sight out of mind...

By the way, in case it matters the mileage has been about 90% highway. She has an 85 mile round trip commute every day. I have not yet brought it to a mechanic for diagnosis (still looking for an honest one in my area).

Any thoughts would be appreciated.

Anyone????

What rpm is the engine at at 55mph in OD? Try to duplicate those rpms in drive on the secondary roads (obviously you will be at a slower speed). Lightly press the throttle and see if the surge is noticeable. If so, then the problem is probably not transmission. If so, you may have a lockup torque converter issue. If not, then it sounds like a load-related issue on the engine. Maybe you have a bad vacuum line somewhere or engine miss due to a bad spark plug wire. You may also want to pull your EGR valve and clean it and the passages to see if that helps. And, anytime I experience a surging engine that doesn't quite seem like a vacuum leak or engine misfire, I run a bottle of fuel injector cleaner to see if that helps. Quite often the injector cleaner cures the surge, and it never hurts. On my own vehicles, I put a bottle of injector cleaner in at each oil change.

-Rod

ive noticed on a lot of newer ford vehicles the TCC will slip if the tranny fluid needs to be changed. my boss swore up and down it was a misfire but i checked all the monitors on his truck and none of them had regular misfires. we flushed the trans and it hasnt done it since. also we have done it on many of the trucks that are on the lot along with a few of the cars. might try flushing it and putting in the MERCON V that it PROBABLY (99% chance here) recommends and see if that takes care of it. flush+filter its worth a shot.