I have a 1998 Dodge Ram Van B1500 with 105K miles driven- great van. I am running into a problem when I am driving usually at about 40mph, but can be in the 50's and 30's, where when I start to climb a hill and so am naturally loosing speed, and before the van shifts into a lower gear to get more power, I get some hesitations where it feels like a super-brief loss of power. It most notably happens then, but can happen when I am not on a grade as well. I will feel it about 4-6 times in about 10 seconds before the shift to a lower gear takes place (if going up a grade). It doesn't happen every time either, just most times when I try to take it easy on the car when climbing a grade (vs. aggressively climbing a hill by stomping on the gas and shifting it into a lower gear where there is no power issue). It also happens when I very slowly and gently push the accelerator while the car is not under high torque and on relatively flat ground. I have also got check engine lights (non blinking) recently: P1494 - Leak Detection Pump Switch or Mechanical Fault- which may or may not be related.
As a summary, this hesitation problem is happening when I slowly push the accelerator while “undergunning” the engine/autotransmission (low RPM).
I have kept this van fully serviced and in top notch running condition. Any ideas? Huge thanks.