Ok, so I don't actually have a problem...anymore. I own a 2000 4-door 2wd 4.3 vortec blazer with the csefi system. At 172,500 miles, it started to run rough when first started. It would idle fine, but it there was hardly any throttle response through first gear. Then about a week later, it shut down without warning while driving. After a few minutes of searching, I discovered the ECM-Ignition fuse had blown. I replaced it and the blazer ran fine for about three days, then the fuse blew again. This cycle repeated for about three weeks, and eventually I was going through 3 fuses a day. Finally, it simply would not start.

In an attempt to fix the problem, I changed the fuel pump, and all related harnesses in that area since every time I turned the key to 'run,' the ECM-I fuse blew and I could not hear the fuel pump engage, and I needed a new sending unit anyway (I thought there may have been a short in the pump or in the surrounding wires) This did not solve the problem. After allowing myself a 1-week 'cool down' period, as I was furious with the vehicle, I started searching under the hood. First I checked all of the connections within the fuse box, which looked absolutely flawless.

My next theory was that I had a bad ground, most likely one linked to the injectors, since the ECM-I is also linked. After deciphering the wiring diagrams in the Chilton manual, I decided to check the MAP sensor, and to my amazement, when I attempted to remove the sensor, it came apart from the bottom...

It turns out one of the clips that holds the sensor down is broken, and the vibration from the engine had disintegrated it. $520 later (new sensor, battery, fuel pump, wire harnesses, and 3m tape for the sensor), my automotive friend is back on the road and doing great.

The loss of power issue ended up being due to a massive buildup of junk on the MAF sensor, which was delightfully easy to clean. I'm just glad that I finally have it running the was I desire: like new.

 

Thanks for posting.
Never know .. someone may be going through the exact same thing

 

No problem, and that's what I was thinking. I searched for days, trying to find someone who had had an issue at least similar to mine, without any luck. None of the mechanics I know had ever even heard of a problem such as mine! Hell, I outsmarted two of them by arguing that I was having a grounding issue, as the MAP sensor is interconnected. They claimed it was either the ignition switch or my sound system (1,500 watt amp & two kicker compvr 12"s)

 

I have nearly the same problem. The differences are that I can still hear my fuel pump activating and the fuel gauge goes out when the fuse blows. It took me several days to figure out that it was the fuse as I was checking the wrong one. But sure enough if i replace the 15a fuse it will start but then blow. I'm going to trace the wires and see if any are grounding somewhere but I'll also check the MAP thanks to your post.

 

I am having exactly same problems thanx for the post the mechs in these parts dont have a clue and I am already a couple of hundred into the problem