1994 S-10 Blazer loss of power

The past couple of days I've read through everything here I could find and it gave me quite a bit of help but my blazer stills has a problem.

About 5 months ago I bought a 1994 S-10 Blazer with a 4.3L Vortec engine code W. It wouldn't start and after checking fuel pressure found out the fuel pump wasn't working. I went ahead and bought a new AC/Delco pump, pulsator, strainer, electrical connector w/pigtail, sending unit, dist. cap, rotor, plugs and wires, 2 fuel filters, changed engine oil and filter replaced the exhaust from the cat convertor back (old muffler and exhaust was rusted badly). Dropped the fuel tank and cleaned it out and installed the pump and sending unit. Put the tank back in the vehicle, installed one of the new fuel filters in the fuel line and put all the ignition stuff I bought in it. Put a fuel pressure gauge on it and made sure everything was working. I had fuel to the pressure gauge at the schrader valve so it seemed I was ready to fire it up. I tried that and it wouldn't start. I had hot blue spark but no fuel was getting to the plugs. I read in my manual that any problems found with the CMFI unit the entire assembly should be replaced. Well I was short on cash so I pulled the upper plenum and took the unit out, sprayed carb cleaner in the poppet valves and rusty nasty smelling fuel came out. Used some air (low) and blew everything dry and reinstalled it. Put on a new plenum gasket and bolted everything back together. After everything was bolted down and electrical connectors were back together I got in turned the key and within a few cranks of the engine it fired up. I let it warm up while I cleaned up the shop and took it for a drive. Everything was working fine. Drove it everyday to work for just over 4,000 miles then one day on the way home on the highway going up a hill I noticed I was losing power. Never did die but I had to step lightly on the peddle. Anymore than that and the engine rpm's fell. I made it home and when the weekend came I took it back out to the shop and decided to do some testing. Didn't know about this forum but I had the repair manual.....heck I can fix this myself...yeah right. I read in the manual that if the fuel pressure didn't approach 61lbs. on acceleration that the pressure regulator on the CMFI unit was bad and it should be replaced and this past weekend I replaced it. Well after reading through a ton of threads here I found out that its a good idea to replace the fuel line assembly (nut kit). I didn't do that and I really didn't look over the plenum to see if there was any wash. Well it's still doing the same thing it was doing. I put a fuel pressure gauge on the schrader valve and here is what I found out. With the key on/engine off and the fuel pump running I have 60lbs. as soon as the pump shuts off the pressure drops to 58lbs but within a couple seconds climbs back up to 60lbs. I turned the key off and let everything set for 10 minutes and the fuel pressure then was 58lbs. I started the engine and the pressure was between 51lbs. and 58lbs. (needle was fluttering back and forth). I increased the throttle to 2,000 rpm's and the pressure gauge needle flutters between 49 and 60lbs. Around 2500 rpm's and the engine starts to cut out, bog down or whatever. It won't throttle up anymore than that. It starts good and idles good and I can drive it in town but I can't take it out on the highway. I put a vacumn gauge on it and at idle it has 19 lbs/inches? and if I increase the throttle it increases to around 21 or 22 lbs/inches. I didn't pinch the return fuel line to see what would happen to the fuel pressure but I think I performed everything else. I'm really leaning towards replacing the fuel line assembly (nut kit) like I should have done when I replaced the CMFI unit. All the fuel pressure readings stay the same with the engine cold or when it's at operating temp. What do you guys think? Where should I go from here? Sure would appreciate any help you can give me. Sorry for the long winded post but I wanted you to know what all I've done.
Also wondering what would make the fuel pressure gauge needle flutter? Don't believe it's supposed to do that.

Good work diagnosing and solving your prior problems.
The Nut Kit/fuel lines are only a problem if they crack and start spraying raw fuel inside the intake plenum.
You get fair fuel pressure until you need some fuel flow then the pressure starts dropping. Sounds like the fuel filter is likely full of the stuff you cleaned out of your injector poppets. You might try replacing the filter again.

Appreciate the advice Chris.

I re-read my previous post and I forgot to mention that I just put another new filter on it before I did the fuel pressure testing. The new filter didn't make any difference.
I went down the parts store and ordered the nut kit and a new injector electrical connector and when they come in tomorrow I will pick up another upper plenum gasket. At least I'll know that everything under the plenum is new.
I'm really at a loss on what to try next.
I will post back the results after I replace the nut kit and electrical connector.
Thanks again.

golddigger

While you have the plenum open, you might try spraying the regulator & CPI orifices with carburetor cleaner too.

The nut kit didn't come in yesterday so I haven't pulled the plenum yet.

I did some reading and thought maybe I should take off the catalytic convertor and see if thats whats been causing this all along.

So last night at the shop I took off the catalytic convertor and put a piece of straight pipe in its place. Here in my state we don't have vehicle inspections. You could hardly see through the convertor so I thought maybe that was the problem. Nope. Still starts and runs good up to a quarter throttle when it bogs down.
Took the vacumn gauge and hooked it up to the intake manifold and it holds steady in the normal range on the gauge at 19-20 hg. At 2,000 rpm is raises slightly to 21 or 22 hg.
Fuel pressure was the same numbers I posted earlier. Fuel pressure gauge needle is still fluttering too. Hooked the gauge up on my friends dodge mini van and it holds steady doesn't flutter so the gauge isn't at fault.
Don't really know what direction to turn now.
I guess I should have spent the money and let a shop check and fix it. Hindsight...I know. Hoping the nut kit comes in today and I guess I'll give that a try and also clean those poppet valves while I'm in there.
Any other suggestions? It's the only vehicle I have to drive.

I ended up taking my S-10 Blazer into a shop and have them fix it.

They found out that when the engine started to bog down that loud noises were coming from inside the fuel tank. They pulled the tank and along with a faulty fuel pump the inside of the tank was loaded with crap. All this combined to make my fuel pressure gauge needle flutter like wild. They told me when they had it hooked up to their machine that when they sprayed carb cleaner through the intake that the engine rpms increased and thats what led them to the gas tank and ultimately the fuel pump.
The pump was under warranty but I guess when the parts store asked about tank contamination the warranty went out the window. After a thorough tank cleaning and installation of a new pump and fuel filter its running like new.
I cleaned out the tank as best I could when I put the old (new) fuel pump in it but evidently I didn't do that good of a job. Only lasted a few months before the crap in there took out the pump.
Thought I would pass along what transpired to all of you. Thank you once again for all your advice.

golddigger77