'03 S10 ZR5 4.3 Stalling, hesitating, loss of power

I'm at my wits end on this one. I have a 2003 S10 zr5 with the Vortec 4.3l that for about 3 months now has been hesitating, stalling and has had an extreme loss of power. Sometimes I fear for my life when
leaving an intersection and it decides to loose all power. The truck can move, I can get it to 95+ mph but it just seems to not have any torque. Leaving a light from a dead stop, I can put the peddle to the floor and the truck will struggle to get to speed and eventually we can get down the road.
I eventually got an error code "P0327 Knock Sensor 1 Circuit Low Input Bank 1 or Sensor 1". After fighting with the dealership they finally replaced the sensor at a discount to me, the truck then ran great for about 3 days. After 3 days the truck started back in with hesitating and stalling and the check engine light was back on with the same code.
Autozone's pocket diagnosis book says to first check or replace the sensor, then check fuel pressure and finally check for an internal engine condition that would cause knocking.
I don't believe the engine is knocking, at least I don't hear or feel the knocking.
Does anyone have any clues or pointers on this? Has anyone seen this before?
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snipped-for-privacy@gmail.com wrote:

Assuming the knock sensor is good? replace the fuel filter, a partially stopped up filter can cause all sorts of problems, next re-check the fuel pressure, after that check the voltage at the fuel pump, as low voltage at the pump can cause your problem, if you do have low voltage at the fuel pump? then check the fuel pump relay? also low oil pressure will shut off your fuel pump, GM has had several factory recalls on fuel pumps, check and see if your vehicle has had a recall? Also the 4.3L has a fuel distribution box under the intake manifold that causes fuel related problems, this unit is expensive, GM now offers a repair kit for this at a much reduced cost. To answer your last question, engine PING is engine knocking, try a higher octane rating fuel, or use an octane booster, with a fuel cleaner. Today many driveability problems are fuel related problems, due to low quality fuel, 87 octane gas is not even good for your lawn mower, why use it in your car engine? Timing is not adjustable on the 4.3 engine, having the PROM chip re-flashed has solved some problems for lots of folks. Car makers don't like to admit they have Bugs in their prom software, they just advise a re flash to get newer updated software in to the older prom chips. A last word of advice, fuel pumps were installed in the fuel tank for two reasons, due to the heat generated by higher fuel pump pressures, reason one was to Cool the pump, reason two was to lubricate the pump, so if you run on a quarter tank or less of fuel? you defeat both purposes for the fuel pump, not to mention the fact that any trash in the tank is in the bottom of it. so run a half to a full tank of gas to help the pump last longer and operate better. Fuel pumps returned as so called Defective? are re tested at the factory, guess what? 90+ percent of them test Good, a new fuel pump bench test machine is in the works for later this year, it will be available at better parts stores, it can test for both fuel pressure and fuel volume, and can also be used to test new pumps before installation. Good Luck
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Nice comment BlackBelt. There is another reason that pump is in tank, it is to minimize the chance of vapor lock because fuel under pressure has a higher boil point and with line from tank pressurized there is no low pressure suction side line to flash easily to vapor when it is hot. You are also correct that low fuel shortens pumps life. On bench testing pumps though, sometimes they can check good for a few minute test but degrade after it runs for a while and heats up and bench tests are seldom long enough to catch this. On the fuel octane, you are correct that 87 octane is really a bad choice here especailly in warm weather. The knock sensor will attempt to listen for knock before you hear it and then retard spark to controll it but it doing so it can really effect performance sometimes. There is two kinds of knock, "ping" or preignition where mixture ignites on its own due to compression , tempature and fuel octane. Spark timing plays no role in controlling it because the spark is not lighting it off. The second is detination and this occurs when mixture exploded rather than burns. This happens when it is lit off by spark and the mixture is at a critical pressure and tempature for the octane of fuel and the flame cascades suddenly through mixture quickly and it effect detonates. Knock control can control this because it retards timing so that spark occurs later and peak critical pressure and tempature is not reached (because piston is started to travel down sooner realtive to ingition so average peak pressure is lowered) and therefore detonation is avoided. The problem is that this also reduces tha amount of energy capture from fuel and power output can suffer a lot at times along with MPG. The only reason there is a knock sensor on a engine is to limit consumer complaints for low octane gas. Where it not for 87 octane, most engines would not even need one. ----------------- TheSnoMan.com
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My 93 Cadillac had a knock sensor and it specified 91 or better octane gasoline.
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Yeah, but your Caddie was probably a diesel. All you had to do was order the gasoline version with shorter gearing, but nooo....
Toyota MDT in MO
(intentionally Snobtuse)
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Shorter gearing, taller gearing...
What the fuck is with that guy, can't he keep lower ratio and higher ratio straight in his head?
(anxiously awaiting Snojerks lecture)
Hey C, you getting lots of AC work?
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Surprisingly, no, but the condenser jobs are becoming more prevalent than in years past.
Related: I am looking into getting a cheap A/C vacuum pump for home use as previously discussed. Have you heard anything pro or con about the FJC line? They have several 2 stage units in the $150 range that are rated at 75 micron, but I'm curious if '75' really means 'about 75 on it's best day, really more like 125'. Some of the Robinairs are nearer a 25 micron rating, but they are in the $300 range. The tool budget is getting tight! NTX Tool Warehouse has better prices and more info on these than SJDiscount, if you wanted to look them up...
Toyota MDT in MO
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Haven't heard anything bad about them.

125 micron is a pretty deep vacuum. 500 and not rising above 750 is sufficient assurance that the moisture is gone.

My theory on Robinair (OTC), they make great hard tools, pullers and such, but it seems that as soon as it involves an electrical wire, they screw the pooch. I'd buy from White Industries before I'd buy from Robinair. Cost no object, I'd get the Inficon Shark and I may well do that if the vacuum pump in the R-R-R machine ever craps out.

I think you'd be better buying the 5 CFM FJC and spending another $150 on a micron gauge, that way you know if there's a leak and you know the system is dry. here's the one I have; http://www.omega.com/pptst/DVG-64.html
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Inficon seems to be the shiznit these days. I bought their handheld heated diode unit last year and it blew away my old Tif Super Scanner on first use.

Thanks for the link. I have been waiting for micron vacuum gauges to come down in price. For the time being, the sniffer and dye are working well; it would be nice to watch system pressure rise in such small increments though. I always laugh at the use of a standard low pressure gauge for determining pressure rise as was taught in class and textbooks. It was only a few years ago that I found out about the micron doohickies.
Toyota MDT in MO
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