Alright this is what I have just bought a 98 blazer with 83k miles on it. Sometimes it is stalling and all the gauges go out and the lights in the dash come on. It is a really quick thing with the tach jumping all the way to 6 and then to 0, and it keeps running. Im thinking its something electrical because the clock on the radio resets when it does this and the tailgate glass is opening as if I hit the hatch button. Its really wierd and i have never seen anything like this before. It will do it over and over with the tach bouncing around and all the lights coming on, but if you ride the brake and gas you can almost keep it running, but it will eventualy die. Then you have to put the gas to the floor and crank it to get it started. It has only done this when you first start up and take off, before i make it out of a parking lot, and so far has not done it any other time. I just had a new ignition switch put it thinking this was the problem, but it did not solve it. Its not throwing any codes and runs fine once you get it going. Just worried this is gona happen when im trying to make a left turn at an intersection. I was thinking that maybe it has a bad ground somewhere but I cant figure it out. Any help would be great.

 

Tug test is a viable and professional method of finding intermittents.
Start with all pos and neg leads from batt terminals. Check for poor connction even inside the terminal crimps.
Only thing in common {considering liftgate circuits /body control module} is the underhood fuse block so after you do all the main pwr and grds, do a tug and wiggle test of the harnesses coming out of the fuse block while the truck is running.

 

Tried both cables coming off the battery and the fuseblock in the engine compartment, no dice. I can not get it to replicate the problem its starting to drive me nuts.

 

Try checking the leads to and the ignition switch itself, you can start by jiggling the key around with the engine running and see if that does it, if not take the column covers off and locate the ignition switch itself (I'm unsure of what exactly it looks like I'm just going off of memory of things i've read on this site) I do know it is attatched to the column and has a bar of some sort that goes up to the lock cylinder. You can then check the wiring and connector on the switch as well as the bar that goes from cylinder to switch.

 

I dont think its the switch i just had a new A/C Delco one put in, and the one that came out looked like it was brand new. Im guessing the guy that had it before me had the same idea. The thing that is making me think something is grounding or shorting out is that the clock keeps resetting when ever it does this.

 

Now go around tapping with a screwdriver handle. Around and on the fuseblock and PCM and wiring harness, esp from PCM and around back of engine.

 

Is the PCM located next to the fuseblock in the engine compartment? Thanks for the help guys

 

Check out your battery health, On my 2000, every time the battery is re-connected, the hatch releases and of course the radio is reset.
Could be your battery is weak (or still a bad connection).

On a dying battery/poor connection the system voltage can dip low enough to reset modules and still crank.

 

Well went out the other day and the car was just dead, so i poped the hood and started messing with the negative battery cable and i started to hear the key chime go off. Jumped in and it cranked right up, so when i got home i pulled off the terminal to check for corrosion and it was as clean as new. I did notice that the negative cable has two raised areas on the cable and that there was nowhere on the battery post for them to go into. It is an aftermarket battery and was wondering if anyone knew if a A/C delco brand battery had detents for the raised areas to go into, or if this might even cause the problem.

 

Hey I think you got a big clue. Check that entire - cable. It has nothing to due with the dimples at the terminal. Also not sure if you put the ignition switch yourself but sometimes after markets are not as oem as they say. Get under there and unbolt and rebolt were the starter switch harrnes connects to the main harnes, this worked for me once. Good luck!