i've been noticing random miss-fires while under load, usually when i have to press the pedal about half way. idle seems fine, and while in park and neutral it revs up good. By random, i mean, one day it does it through the day, and the next it runs like a champ. cap & rotor & plugs are fairly new as i changed them out when i first noticed it. Also, im getting that rich smell, especially when i first start it up, after a while the smell is not as bad but its still there. the fuel pump was replaced about 8months ago with an ac deco pump. spider and nut kit about 3yrs ago, nut kit was ac delco, spider was after market as ac delco was way too pricy and was a special order. i have a feeling there is an issue inside the plenum again because of the rich smell, its just a pain to remove it to check and want to make certain it is before trying to remove that thing again. today, checking the plugs and cap & rotor again, i took it for a hard test drive and it ran like a champ but i did feel a miss-fire or two, got home and let it sit and about 2hrs later went back out to the blazer was bogging in reverse and in drive, went around the block and came back home cause it was feeling funny. glad i made home because once i parked it, i rev'd it up and hurt a muffled backfire so i let go the gas and let go back to idle and I turned it off, but now it wont turn back on. it cranks and cranks but nothing. can't think of anything else to check right now. help me obie one kanobi, you're my only hope

 

Maybe your cat is stopped up the symptoms seem to point that way

 

oh i forgot to mention that the cat and muffler was replaced 4months ago as well. and no SES light or codes in memory.
BUT....

This morning it fired up right away, and i drove to work, about 25miles, all street and it ran good. i got the smell of when it runs rich, but when i got to work i got that smell like when you just installed a new cat and muffler. THis is very wierd and hard to pin point where the issue it.

 

Just a guess (I'm working on a 95 blazer now) but probably a short somewhere on the wiring harness.

The insulation on quite a few wires on my harness isn't looking too good so I can see where a short can happen pretty easily.

OR if you had any aftermarket add on like an alarm system try to disconnect it and see if that doesn't fix the problem.

 

just did a fuel pressure test

key off the on: jumps to 59psi
once pump shuts (after 2-3 seconds) drops to 44-45 psi
10min later: 32psi

these results must mean that there is an internal leak in the Plenum, right?

 

The test results mean there's a leak somewhere. To find out exactly where you need to test fuel pressure on both sides of the filter. That will tell you if the pressure loss is due to a bad fuel injector assembly (spider) or a bad check ball in the tank. There's a writeup somewhere here on the forum about how to do that test. I've used it several times myself.

 

yeah but if it was related to the pump, the blazer wouldnt be running rich, i couldnt be in an underground parking lot for too long with the car on because the smell.

FYI:
This morning as I was driving to work, it bogged on me several times, so i said the hell with it and stopped by and picked up a regulator instead of the full spider since the spider cant be returned cause its considered a special item, got home and pulled the plenum, sure enough the passenger side was almost spit shine clean while the driver side was full of carbon build up. even the regulator was super clean. the wierd thing is that with the plenum off i turned the key on engine off to see if i can see where its leaking and/or spraying and nothing was coming out. Im assuming that it only leaked while running since i couldnt catch it when turning the key on.

any who, replaced the regulator installed everything back and fired it up. Turned on super quick, and the exhaust sound was much better toned than when before replacing the regulator. drove to work this time on the freeway(highway) and the throttle response is much smoother and the pick up is a lot better. punched once i got into the freeway and it took off like a champ with no bogging/misfiring. hopefully this will be the end of the rich smell, which was noticeably less in the when i first turned it on.