Hey, I searched through the posts to try and find an answer to this problem, but was unable to find a similar sympton to compare.

My brake pedal feels like it would if you pump the pedal with the engine off... but its doing this while the truck is running. At the same time (when you put all your strenght into it to keep the truck still at idle) the engine seems to be strained to the point of stalling. My wife is the one who drives the truck, which is not safe for her at the moment. If anyone has any idea what I should look at replacing or any ideas, I would appreciate it.

Truck: 97 Blazer 4WD

 

I would bleed the brakes and check it again.

 

Check for a vaccuum leak, especially coming from the brake booster.

 

WOW....you probably need a new vacuum brake booster. Check the ability of it's check valve to hold vacuum by running the engine for a few minutes and them shut it off and pull the large vacuum hose out of the brake booster (make sure you pull the black plastic fitting out of the grommet with the hose). If You hear a sudden sucking sound, itis air rushing into the booster to equalize the pressure, and the check valve is good. If it is good youhave a busted diaphram in the booster, and you will need a new booster assembly.