1994 S10 Blazer 4x4 4.3L "W" Auto 162k miles

[blazerchase]

I have been having mild issues with power through full rpm range. I noticed problems with shifting: when I was barely pressing on the pedal from a stop, it would not shift until I got to 25 mph. I cleaned some obvious carbon build up off of my IAC valve, and the problem went away for the most part. Within a month it randomly came back, but with a new issue. It would not want to stop and idle. I would be going 40 mph on the freeway in traffic, take my foot off the pedal, and it would not slow down. It also had mild surges that were either consistent or not happening at all.

My engine was running hot on the freeway as well (210-225 degrees). I replaced my water pump, which has been leaking out of the weep hole for up to a year or more, along with my fan clutch, thermostat, and the dealership said that they "rodded" my radiator because it was 80% blocked up. After all my work on the cooling system, my vehicle gets up to 235 degrees every time it warms up for the first time, and then stays between 210 and 220. I am used to it always staying below 200, and when I really push it, seeing it go to 210.

I mentioned all the above just to troubleshoot the current problem I am having, since it is most likely related some how.

My car started to stall on Friday, and had no power. It would start up fine, and then only accelerate a little if I barely touched the pedal. I had my cat check out by a decent shop, they said it was good. I limped home, but on Saturday, my car would not start. I have zero fuel pressure, so I changed my fuel filter. It took a little to start it, and it ran with the same problems as the day before, but then two blocks later died. The fuel pump was making noise, and I even heard it start to "fizzle out on me", just before it quit completely. The fuel pump relay clicks when I turn the ignition, but I have not heard the pump working.

I dropped the fuel tank today, and have a 4500 lb paper weight in my driveway.

I need help in figuring out how to fix it in such a way that I do not have to do this for another 150k miles. I am strapped for cash, but willing to pay for reliability as well as proper diagnose of the problem.

I would like some tips on bench testing the old fuel pump, but I am going to replace it just because it is out, and I am pretty sure it is the original unit. I have seen complete units and strainers for around $100. (airtex from rockauto.com) but I don't want to blow my money on crap.

Please Help

I am tired, and am not going to spend the time to review everything I just wrote, please just contact me if you have any advice, experience, or questions.

I recently replaced my fuel pressure regulator, and cleaned out my upper intake plenum.

Finally, the thing that blows my mind, and hopefully someone can clue me in on:
I purchased a Gunk Octane Booster (orange bottle) a couple week after replacing my pressure regulator, and my car ran incredible. Not just a little better, but AMAZING. Full power through rpm range, clean shifting, as well as great idle.

WTF could be wrong with my engine, that a $5 bottle of "snake juice" could have such an effect? O2 sensor? IAC? MAP sensor?

[old_master]

No doubt it's a lack of fuel pressure. The fuel delivery system must be checked while it's still in the vehicle. Ignition in the RUN position, engine OFF, fuel pump running: fuel pressure must be 55psi to 61psi and must remain above 50psi for 3 to 5 minutes after the fuel pump shuts off. If it does turn out to be a faulty pump, stay away from Airtex, they're junk, don't waste your time and/or money. Use AC Delco or Delphi only. Post your results.

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