Blazer loses power, especially on a hill, no matter how hard you step on the pedal. Recently replaced oxygen sensor and distributor and was running fine for a month or so. Also there is a loud hissing from engine when depressing the pedal but tends to go a away when just idling. No engine light either. Any ideas whats wrong?

 

have u checked spark plugs and wires? see what their like

 

Not yet..plan to give it a tune up this weekend and checkplugs, wires, filtersetc... and take it from there. The car is new to me (but was well maintained before I got it) so I was hoping Iamrunning into something someone has already experienced and save me some frustation trying figure it out.

 

Hissing like a vacuum line, maybe?

 

ya i had the fuel lines inside the plenum go bad on my 94 and i was loosing power i also experienced rough idle at start up and strong sulfur smell from exhaust. so if any of that is true for u i would say head in that direction. but by looking at the spark plugs u could see if it fouling them out or somethin and that could help lead u into the direction of ur problem. and the hissing could be a vaccum line like rriddle3 mentioned

 

A vacuum line was my first thought. But the noise seems low in the engine compartment ...exhaust maybe?

 

I've never heard a hissing from an exhaust. Roaring, popping, ticking...yes, but not a hiss.

 

if u describe the noise as a hiss its gotta be a vaccum leak. vaccum hoses run lower in ur engine bay if u have 4wd cuz they go to the transfer case. and a hiss is def not coming from the exhaust u would hear popping like u have no exhaust and the exhaust will get louder if u have a hole in the exhaust.