Engine losing power over hills

A lean fuel mixture can be caused by a few things. Have you checked fuel pump pressure? Have you checked for engine vacuum leaks?

This guide will help

https://www.2carpros.com/articles/engine-has-low-power-output

Please run down this guide and report back.

Since the mixture is lean, I would suggest checking it. Also, has the coolant temp sensor been tested?

If I don't hear from you, Have A GOOD CHRISTMAS!

The transmission position sensor got wet which is causing the problem. Remove the connector and use compressed air to dry it out. If this doesn't work I would replace the switch

Here is a diagrams of where the switch is (below)

Please let us know what happens so it will help others.

Cheers

Does your have the same problem with the transmission lights? If not check out this guide.

https://www.2carpros.com/articles/engine-has-low-power-output

AND

https://www.2carpros.com/articles/crankshaft-angle-sensor-replacement

Please let us know what you find.

Cheers, Ken

I do not understand much of your terminology, but I get the impression the engine is stalling when you slow down after driving for some distance. A stalled engine will result in loss of power assist for the brakes, so that is to be expected. You will still have brakes, but you will need to push much harder on the pedal.

If it sounds like I have the description of the symptoms correct, an elusive cause is a collapsing or plugged pickup screen inside the gas tank. Depending on the type of fuel delivery system your car uses, many of them pump a much higher volume of fuel when the car is coasting and slowing down, so that is when the plugged screen causes the symptoms. Most of that high volume of fuel goes right back into the tank, but the restricted screen causes fuel pressure to drop.

To verify if I am right, you need to attach a fuel pressure gauge so you can watch what happens to fuel pressure when the problem occurs. This has happened to me three times with two cars. In the second one, normal fuel pressure varies between forty five to fifty five pounds, and the symptoms showed up when it dropped to less than twenty pounds. Some engines will not run when the pressure drops just five or ten pounds. I run the hose for the gauge under the rear edge of the hood, then I clip the gauge under a wiper arm where I can see it from inside the car.

The additional clue is that screen will stretch out again and let fuel pass if you let the car sit on the side of the road for ten minutes. With my car, I could drive up to about another five miles before the problem occurred again.

You need a scope to check it. Would be easier for a shop to verify it for you.
It cannot be repaired only replaced if it is at fault.
Check the coolant sensor and make sure it is working correctly as well.

Roy