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Sluggish accelration

I own a used 2006 Chrysler T&C which is still under warranty. I bought this low mileage vehicle from a local dealer. This minivan is equipped with V6, 3.8L engine, which I thought, will be better one than its 3.3L sibling. After driving around, I experience this sluggish response to accelration. Also the highway MPG is always less than 22. Use Shell gasoline 87 octane. I have not tried higher Ocatane yet. Now, the scenario.

There is no problem as long as the vehicle is running a speed of 35 to 40 or 45 miles/hr range. But then the problem begins to occur. When I need to accelrate, and to merge onto the highway traffic, I will push the gas, but the RPM sits around 2000, but does not do a thing to the speed of the vehicle. Few second pass by, and I can hear a roar, and the RPM will go up to 3000 or more to reach the desired speed to merge into the traffic. However, the problem is that the whole process seem like ages so to speak, Often times, it is a very dangerous situation, due to the speed of the oncoming traffic, which can be very close to merge. I took the vehicle to the dealer several times, but they are looking for “codes”. There are no codes at this time. So, they did not do anything. The vehicle will be out of warranty by June 2009. I am hoping that this is minor problem to fix.

What’s happening is your torque converter lockup clutch is “hanging on” to keep your gears in overdrive. This is programmed in to save gas. You need to push the throttle a little more assertively to get the converter to unlock and/or get the transmission to downshift sooner.

You might improve you highway mileage by:
Keeping up with basic “tuneup” maintenance.
Proper tire inflation and alignment.
Remove extra cargo weight.
Proper weight of motor oil - not too thick

Now’s also the time to get the transmission fluid drained and refilled. No flush.

Thanks for the reply. Appreciate the info about the torque converter. Make sense, because it goes to low RPM to save gas. Although it does not seem savin it now. Regarding the maintenance; I followed the dealer recommended services such as: using 5W20 for oil change, fuel service, also the transmission service. Dealer did the flush and fill for transmission. There is no cargo weight at this time. The vehicle is only 23200 miles on the odometer. Welcome any suggestions to improve gas mileage.