3 questions about my 01 Tracker ZR2 --

1: The 4 wheel drive will shift into 4 High but the indicator light on the dash flashes on and off and the 4WD goes in and out. I had my brother squeeze the hose coming off the actuator pump and the light continued flashing. I think this means the actuator pump needs to be replaced. Can anybody confirm?

2: Occasionally during idle and when removing my foot from the accelerator and often when in reverse with my foot pressing the accelerator and/or backing up a hill there is a buzzing sound coming from the engine. It only happens during the times mentioned. Never when moving forward except sometimes when I take my foot off the accelerator like moving forward down a hill, but never when the accelerator is pressed while going forward. No problems with acceleration or coasting or anything like that, just the buzz sound that doesn't seem like it should be happening normally. I've never been able to figure out what this is. Any ideas?

3: Sometimes when driving forward and when I remove my foot from the accelerator the entire vehicle will sort of jerk immediately when I take my foot off the accelerator. No issues with acceleration or stalling or anything, just sometimes a jerk or jolt sort of when taking my foot off the accelerator. Any ideas what might cause that?