hey, I've been using this great forum as my "blazer guide" for some time now, so i decided to finally register... anywho I have a 1994 Chevrolet s10 Blazer (LT 4dr, 4wd, tahoe 232,000mil. 4.3l vortex) And it has its own little qurks here and there but this one is kinda a biggy.....I recently had all the vacuum lines replaced, battery, starter. The truck has NO exhaust at all (just the pipe from the manifold and ends right above the passenger side door) So i don't know if that originally caused these problems to happen but anyways for some reason whenever i go from "P" too "D" or "1" "2" or overdrive the engine will stall...unless you give it some gas when changing gears.... It even stall's if I'm idling at a red light or idling in gear (so i have to drive with two feet) So theirs one problem, Now to the next... well this one is a lot more serious. As of right now I can't drive it because the oil psi gauge is going crazy...I was driving up a decently steep hill on my way home from school and it was between "0" and "40" which is not normal for it (its usually a little over 40 when driving up hills or higher rpms) and then when i got back to my house the gauge was bouncing up and down when idling and would drop if i pushed down on the accelerator (not good) and when I turned off the engine I heard a hissing noise so that's why I'm here to ask you all thats up with "da blaza" (ps. i over filled the engine oil a little over the "hashmarks" on the dipstick so I don't know if that would come in to play with this problem) like i said any help would be appreciated and sorry for such a long story

 

The hissing sounds like a vacuum leak to me. You get the most cvacuum at lower RPM, so thats why you can hear it when you switch gears and the RPMs come down, You might want to invest in a couple tools, one being a vacuum pump that will alow you to check for a leak with the engine not running, and the other would be an oil pressure gauge so we can get an accurate reading of running pressure, you could be having some issues with the oil pressure reading due to a crappy connection at the sending unit. As for the stalling, it wouldnt hurt you to remove the EGR valve and clean all the crap inside it out, Im guessing it stalls but restarts just fine. Check out these things and see what you find, dont forget to let us know what your results are. Welcome and glad you stopped creeping the forums and joined us. This is the best place online for help fixing these trucks.

 

Thanks for the helpful reply!....Yes you are correct, when ever it stall's she'll firer right back up....due to the engine being very loud I cannot hear any hissing noises, All i hear is..well.. The ENGINE :P So when shut off I can hear a slight hissing but go's away after a few seconds....my step dad (previous owner) believes that the oil pump is going bad and thats what is making the gauge go crazy and he says the engine is hissing because its over heating because its the oil pump (I disagree with that) so what do you'all think of it?.....I like to believe its ohsofly's guess's......anyways..thanks ohsofly for the post and everybody here ....anymore info would be great!