Hard to diagnose electrical issue!!!!!!!

I own a 93 S-10 Blazer 4x4 w/4.3 Vortec. My problem is this: Over the last year is has been getting harder and harder to start. I'm about sure my fuel pump is beginning to fail. A fuel pressure test will verify this is the next week or two. Anyhow, intermittently, my truck will not let me get past 2000-2500 RPM. When the truck is in nuetral, it revs fine, but when in gear, it struggles and almost feels like it's not wanting to kick down, or better described as taking off in 5th in a manual, when you're meaning to hit 2nd or something. My engine and transmission are completely fine. When the problem doesn't occur, my truck runs great! Also, when the problem occurs, my digital speedometer reads 188. The only time it's supposed to do that is when you first key the ignition. It's almost as if the ecu is rebooting. That's normal, but not when you're driving. Could this be a failing speed sensor, or ecu? Where are the ecu's located in these things? I've checked all kick panels, and peeked behind the glove box... NADA. All my grounds are tight. I did check that.

Also, I am getting no codes. but it does flash 12 when I shoot them. That indicates my diagnostic function is working... And, while it's in park, if I hold the pedal steady at 1000 RPM, it fluctuates a bit. I just replaced wires and ignition coil. I just don't get it, it's a good running vehicle when it's acting right. No misses, no lack of power... NOTHING. I'm stumped!

Welcome to AF! I hope we can help.

It sounds like you're losing ground or possibly power to the ECM. Check the fuse connections in the fuse panel for the ECM. Check power feed connections at the fuse panel and battery cable connections, both at the battery and at the engine. The ECM is located either behind the glove box or behind the passenger side kick panel.

Welcome to AF! I hope we can help.

It sounds like you're losing ground or possibly power to the ECM. Check the fuse connections in the fuse panel for the ECM. Check power feed connections at the fuse panel and battery cable connections, both at the battery and at the engine. The ECM is located either behind the glove box or behind the passenger side kick panel.

I checked the ecm fuses, and they were good. There are only two spots to the motor where grounds are connected. Battery to exhaust manifold (It's tight) and drivers side intake manifold to firewall (tight as well). I also disconnected them all, sanded them clean, and reconnected them. I will remove the fuse panel tomorrow. Could a failing alternator do this as well? I mean, with all accessories on, it's putting out a 13.5V reading. Thanks for the prompt response, I will check this tomorrow. Guess I'll just remove the fuse panel housing to inspect it.

When you checked the ECM fuses, did you pull them out and check the terminals inside the fuse box? Could be a poor crimp or worn terminal on the back side, so pulling the fuse panel may not be a bad idea ;) Alternator voltage output should ideally be 14.2 volts, battery fully charged, and accessories off. It's normal for voltage to drop slightly with a load, lights, HVAC blower etc.

When you checked the ECM fuses, did you pull them out and check the terminals inside the fuse box? Could be a poor crimp or worn terminal on the back side, so pulling the fuse panel may not be a bad idea ;) Alternator voltage output should ideally be 14.2 volts, battery fully charged, and accessories off. It's normal for voltage to drop slightly with a load, lights, HVAC blower etc.

Actually, it stays at 13.5 when running accessories or not...? I did not use a digital meter. Also, is code 12 normal when checking codes? I got a code 54 as well, but when my truck is running, no check engine light. Does that mean these codes aren't being stored?

This may help: http://www.freeautomechanic.com/diagnostictroblecodes5.html

Here's a video I made of my truck trying to show ya'll some of the issue. Please excuse the poor video quality if there is any!

http://www.youtube.com/watch?v=fpLGHUXo5_8

Quick Note: I thought pressure was supposed to be retained in the fuel line, before/after the filter, right? Well, after I took the nuts off the filter, no pressure was present. I figured I'd get sprayed or something. It only poured out after I removed the in/out lines. No pressure at all.

There is excessive leakdown in the system. Having to spray either to get it started is a classic symptom of excessive leakdown. Pressure must remain above 50psi (93 CMFI) for 3 to 5 minutes after the pump shuts down. Cycle the key several times before cranking and it may reduce cranking time.

Engine temp looks a little low too.

Fuel looks a little dark...wtf?

Fuel looks a little dark...wtf?

More than a little!

More than a little!
But this was just the fuel that was before the fuel filter, it didn't look like that after it pass thru the filter... lol

But where are you getting fuel that nasty? And can you really be sure that's not causing any trouble?

But where are you getting fuel that nasty? And can you really be sure that's not causing any trouble?
It's not where, but how rather... Where I live, my truck takes a beating every time I leave the house. The driveway is 7 miles long, rough rocky roads that will eat tires for breakfast, and I have to cross a river, and stream... That's just one way. It takes nearly 40 minutes to get to the paved road. As for what's causing my problem... Well, that could be a number of things. I'm sure the gas is getting that way because of the terrible beating my truck takes, and the vibration it goes through. I'll be cleaning out my tank when I get my new Delphi setup.

Just like my old '93, I wish I kept it, that was a solid truck.

The speed bumping up like that when your revving it is normal, and the bounce in idle when your revving it at about a thousand rpm's, actually its around 850rpm, is also normal, my truck did both those things too.

Fuel pressure problem, either your fuel pump or your regulator under the plenum. I am betting its your fuel pump becasue you mention that you can't get past 2500rpm under load, probably becasue the pump cannot maintain the needed pressure and you just leaning out the engine - a dead gas pedal. Get a fuel guage on there.

On a side note, and not that much of an issue, but your ground strap was originally located on the front of the engine block, just under the exhaust manifold, not on the exhaust manifold itself..... to bad you weren't closer, you could have my box full of fuel spider parts for this truck. I have, I think about 3, or 4 of them.

Just like my old '93, I wish I kept it, that was a solid truck.

The speed bumping up like that when your revving it is normal, and the bounce in idle when your revving it at about a thousand rpm's, actually its around 850rpm, is also normal, my truck did both those things too.

Fuel pressure problem, either your fuel pump or your regulator under the plenum. I am betting its your fuel pump becasue you mention that you can't get past 2500rpm under load, probably becasue the pump cannot maintain the needed pressure and you just leaning out the engine - a dead gas pedal. Get a fuel guage on there.

On a side note, and not that much of an issue, but your ground strap was originally located on the front of the engine block, just under the exhaust manifold, not on the exhaust manifold itself..... to bad you weren't closer, you could have my box full of fuel spider parts for this truck. I have, I think about 3, or 4 of them.
HANG ON TO THOSE!!! lol I would be more than glad to send you some dough via pay pal some time down the road, in case I EVER NEED THEM!!! lol
As for the grounds... They're in a different spot because someone else put another motor in this when I first bought it. Only reason I got it for so cheap is beacue they left the ground loose and it was running like total sh*t. I tightened the ground bolt and it's been running like a champ for nearly two years until this problem!
Here's what it looked like when I first bought it:
http://i2.photobucket.com/albums/y37/indeepshitnow/100_6800.jpg
Not bad for being 15 years old back then! Anyhow, I appreciate your input on my issue... I'll be buying a Delphi in a couple of weeks. That is, after I make sure the pulsator does not need replacing first.

PROBLEM SOLVED!!!
Finally got my fuel pump in today, put her in and she is running like a champ! Cranks right up, and will put you sideways when you floor it... ;) Thanks goes out to Old Master for dedicating his time and patience in helping me with suggestions, etc.!!!
Thanks dude, you rock!

My truck isn't fixed!!! I broke down twice trying to leave TX. Made it to a friends in Houston. Cost me $700 to have 3 wires fixed from the harness in the engine bay, and one under the dash to solve my dash issues. (in ref. to flashing 188) And my truck ran fine for 100 miles, but then started hesitating, backfiring, etc. Replaced Cap, Button, Ignition Control Module, Ignition coil, Fuel Pump, ECU, Wires, none of that really helped. My truck is running lean, the ECU says, and did smoke up until I replaced the TPS today. Now it doesn't backfire, but hesitates badly still. It has plenty of power, but seems like it's missing. It is NOT out of time. Idles normally. Codes 22,23,43,44. Reset the battery, and now I get 23 only. I just replaced the TPS, so it's not 23,22...? Still tryin to pin this down!? Are there any other electrical sensors or such in the dizzy besides the ignition control module? Like, do I have to remove the dizzy completely to find a spark problem? Code 43=Electronic Spark Control fault... Would that make my truck hesitate? Sounds like it. What Controls Electronic Spark?