Chrysler Repair: Car speed slows on interstate, screwdriver blade, penetrating lubricant

Question
At higher speeds the rpms drop and the car slows.
No matter how much gas you give it. Then the car will pick back up. It's a 1999 chrysler sebring with a 2.5 V6.

Answer
Hi Gary,
There are several possible reasons not related to the mechanical functioning of the engine which is a separate level of investigation that you should try second if the simpler items don't yield improvement:
has the fuel filter ever been changed?
might the catalytic converter be partially clogged (this can be tested at an exhaust shop).
have you tried to have the fault codes that may be stored in the engine controller memory readout (Autozone will often do this for free) Get the code numbers, if any, and write back.
might the egr valve be sticking open at full throttle (this might also cause difficulty in starting/idling)?*
how long since the air filter was changed, it is perhaps clogged with dust?
Are the spark plugs pushing 100,000 miles since installed?
Those are the things I would evaluate and try to verify first.
Roland
*The first thing I would do is check the mechanical function of the egr valve which is located along a pipe that runs from the left exhaust manifold (on the side of the engine facing the front of the car) to the intake manifold area (where the incoming air in the large rubber tube enters the throttle). That valve is metal and has a round fitting with a vacuum hose attached, mounted on the top of the valve, and the round part is attached to the main body of the valve by a sort of saddle. Inside the open saddle you will see a metal rod (with a slot) that connects the round top fitting to to the valve body. That rod is a stem on the valve and it is supposed to go in and out in response to the engine vacuum which varies with RPM and throttle opening (gas pedal position). Take a spray can of WD-40 or other penetrating lubricant and spray the stem where it enters the valve body and then use a regular screwdriver blade tip inserted in the slot to lever the valve in and out to try and free up its motion. Also check all the rubber vacuum hoses associated with the valve and a nearby vacuum solenoid valve. If the valve seems to open (against the action of a spring) and close firmly by the spring action when using the screwdriver blade to facilitate the motion then give the car a road test. You can, once it is idling, check that the valve stem moves when you rev the engine from idle to 2500 rpm and back to idle.