4.3 TBI fouls plugs constantly

You guys seem like a well informed bunch. I hope that you can give me some insight. I went back as far as I could in the threads but did not find anything quite like what I'm having a problem with.
I've got a '91 S-10 Blazer with a 4.3 and it's been destroying plugs in about 5-10 minutes (and I'm sure you know what a drag they are to change-center driver side @#$%^&*). It fouls all 6 plugs black, not really oily but they seem wet with gas when I pull them. It doesn't really seem to smoke much but the exhaust has black carbon-like soot at the end. Mechanically the engine seems to work fine. It has about 137,000 miles on it.
I've replaced the coil and ICM, cap, rotor, wires and plugs several times now in the process. I figure it's the fuel injection system or something that controls it (EGR, ECM, regulator, etc.) but I don't really know FI well. I have not been able to get the fuel filter off, it's 10 degrees here right now, and I'm working outside. It doesn't seem like a filter problem though. I've had 4 TBI trucks and have never had a fuel delivery problem before (probably just blind luck).
If it was a carb I'd figure it was running way too rich like the choke was stuck. The last time I got it running I did get a check engine light before it died. Engine starts, runs fast idle for a minute or two then starts missing and running rough then dies. I can't get it anywhere to have it tested because it won't run long enough and I'm getting desperate. I don't find any obvious vacuum leaks.
Has anybody else seen anything like this or have any advice on where to start? I'll probably need to figure out the codes but I'm not sure how without the diagnostic gizmo that plugs in under the dash. I'd be greatly appreciative. It's just a beater but I'd really like to get it running right without replacing stuff blind, like I've been doing... Thanks for whatever assistance you can offer - Russ
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It fouls all 6 plugs black, notreally

One of two things:
1. CTS (coolant temp sensor) is shot and causing her to run super rich. When the sensor dies it defaults to -40*F hence the motor will run way rich. This usually makes it run like absolute shit but doesn't normally cause her to die like yours is.
<most likely scenario is............>
2. FPR (fuel pressure regulator), located inside the throttle body is FUBAR. The diaphram is likely ruptured and she's just dumping gas into the motor.
Regardless, you need to run a scan on the ECM and see what codes have been set. Follow this link for excellent instructions:
http://www.georgiasyty.com/aldl.htm
Regards,
Doc

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It fouls all 6 plugs black, not

I'm on it. I did see something in one of your previous posts about the CTS and picked one up just in case. I appreciate the feedback, thanks - Russ
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I did get the error code off - it was a 44 - O2 sensor exhaust too lean. I suspect that it may be a combination of problems but I'm guessing I should replace that sensor also. I'll start with that then work towards the others, please let me know if you have any other thoughts. I really appreciate the help - Russ
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your O2 sensor is gone
the ECM is receiving a 'too lean' signal and adding fuel to attempt to correct the problem
could be that the wire to the O@ sensor is off or has been roasted on the manifold and shorted to ground
less voltage = lean signal
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Yeppers, my thoughts exactly. Happened on my old Acclaim years ago. ECM said 02 lean, was getting 5 MPG and leaving a black shroud of smoke wherever I went so I knew there was no way in hell she was leaning out.
Doc

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most recently saw it on a 92 GrandAm Quad 4
made almost as much black smoke as a ruptured fuel pressure regulator..............
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You guys rock, I can't thank you enough. Now I just gotta get my fat butt under that thing in the snow and try to get it out of it's home for the last 13 years without screwing up the threads too badly. I doused it with WD40 today, I'll get under there tomorrow and try to get it out. After looking at it, I'm guessing I'll be heating and beating to get it out before it's over. I'll let you know how it goes. Thanks again - Russ
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While at that age it does need to be replaced, make sure to inspect the wires. You may have a 5 minute wire fix (but change the sensor when it gets warmer!)
~KJ~

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I replaced the O2 and CTS unit. The wires I could see looked okay but I got no temp gauge - It's cheezy (I've never seen it work. Haven't had it long. I hadn't gotten that far). It still runs crappy and won't idle after it gets a little warm but will usually restart. I'll probably have to replace the plugs again. I'm still waiting on the fuel regulator repair kit. Any suggestion on how to get the old fuel filter off? I really don't think heating it up is a good plan but it's the only one I got. Thanks for all the help - Russ
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You need to reset the ECM after installing new sensors. Unplug the battery, leave it unplugged for a few minutes, then hook her back up again. Might solve your problem as the ECM needs to learn the new operating paremeters of the new sensors.
CTS feeds the computer, not the temp gauge. The coolant temp SENDER (not sensor!) is located on the side of the drivers' side cylinder head, between cylinders 1 and 3. Single wire connection.
Regarding the fuel filter, HOSE the connections with PB blaster, use a great big adjustable wrench on the filter "nuts", and a pair of vice grips super, duper tight on the line nuts. If you use a flare-nut wrench you'll break it, if you use an open-ended wrench you'll round the bolt off. Vice grips will chew it up a bit, but leave you lots of nut to get it back on. Work both wrenches at the same time and they should come loose.
I've had to cut a few off in my day (Dremmel with garden hose spraying on lines) and just use a nipple-style fuel filter with hose clamps in its place.
Doc

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I bought a Delco O2 sensor, the directions said it already had compound on it. I did disconnect the battery for a couple minutes after I replaced the sensors just in case. If it's one thing I understand it's reset (I babysit computers for a living). When I got under the truck to mess with the filter (thanks Doc!-I'll replace the sender after I pay for this mess) today, I realized I have gas coming down the frame rail on the driver side back by the tank so I got a bigger problem. It sure isn't a sealed system anymore, something sprung a sizable leak.
I think maybe I've hit the end of my backyard mechanical ability. At least backyard in the winter. I don't think I got the means for dropping the tank, and I'm tired of laying in the snow. I'll have to eyeball it again tomorrow but I may have to pay someone to fix this one.
Thanks for all the help, I appreciate all the suggestions/advice. I've got 3 of these 4x4 S10 based trucks, plus a TBI 5.7 van so I need all the help I can get - Russ
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Use a copper based anti-seize:
not the grey stuff which is made of glass.
You'll get a better contact to ground and a better O2 sensor life also.
Refinish King

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the 'stuff' that's on the threads when it comes out of the box is the proper thing to use
it's conductive
message

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I find a good way to dispell any question is to:
backprobe the O2 sensor connector with a good DVOM, and check for diddling and an average if the meter I'm using has that feature.
That's the first test I make. Then use some propane to spike the sensor, a good one will spike over 1.2 volts. a bad one won't go over .8 volts.
I hope this helps
Refinish King

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