96 Tahoe dies while driving and won't start

[eyesi]

Backfires thru the intake, you should suspect timing.Retarded spark timing can cause backfiring through the intake.
Also, are spark plug wires well routed?

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Exhaust restricted, you can put a low scale manometer in oxigen sensor hole.

VCM (powertrain control module) grounds and power circuits test must be checked if other mechanical issues are fine.

VCM connector 1 blue, 2 red, 3 clear or gray and 4 black.
http://troubleshootmyvehicle.com/gm/4.3L-5.0L-5.7L/pcm-connector-pin-outs-1996-1997-page-1

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check ground wires at VCM blue connector pin 17-18 , if you get no a lecture near to zero ohms there, with battery positive disconnected, then ground that 2 pins, if you want near the connector. When they said check computer grounds , check them at the end of the VCM or PCM or ECM connector is the only way reliable to me, and is a very very common issue at computers related failures

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[jlcms2007]

You are correct. If the injectors are pulsing then the distributor is turning. If there is gas coming from injectors and you have spark at the plugs you definitely need to check compression and cam timing

 

[Nightflyer]

Okay....

The compression-test. Here are the results:
#2: 160psi #1: 170psi
#4: 175psi #3: 155psi
#6: 170psi #5: 160psi
#8: 170psi #7: couldn't test it in case of a broken arm...(

So turned the crankshaft by hand an aligned the markers on the balancer with the mark on the engine (top dead center cylinder #1)

Here is the picture from the rotor (i've tested my old one...). The contact is not at the marker of the housing from the distributor (there's a little number on it...6 or 8 eight...i don't know for sure) in the bottom of the picture.






But i think i make an mistake: i've not turned the balancer clockwise....is that very important??

The spark plug wires are all well routed.

Tomorrow i'll check the ground wires of the VCM.

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[eyesi]

But i think i make an mistake: i've not turned the balancer clockwise....is that very important??
It is very important, no turn it CCW, even a bit, do 2 crankshaft turns more if you pass the mark .

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[Nightflyer]

OK...stupid question: what does it mean: clockwise in front of the engine (when I'm standing in front of the car) or clockwise when i sit in the car...*confused*....

Could i damage something while turning in the wrong direction?

What's about the results of the compression test and the distributor? Jumped time?

 

[eyesi]

OK...stupid question: what does it mean: clockwise in front of the engine (when I'm standing in front of the car) or clockwise when i sit in the car...*confused*....

Could i damage something while turning in the wrong direction?

What's about the results of the compression test and the distributor? Jumped time?

see rotation of balancer when engine is cranked, that is the correct way, no, you don t damage anything if turning in the wrong direction

 

[Nightflyer]

Ok....

I've checked the distributor cap: the rotor on the picture is at #1.......

What's going on? Compression might be okay, right?
Distributor/rotor position seems okay, right?

What the hell....

 

[LostX]

Pull the distributor and look at the gear. It probably skipped a tooth.

 

[skylark]

Ok....

I've checked the distributor cap: the rotor on the picture is at #1.......

What's going on? Compression might be okay, right?
Distributor/rotor position seems okay, right?

What the hell....

Compression is fine. Do you have spark on all 8 cylinders? Vortec distributor caps are known for being crap. Are the plugs getting wet from fuel? Are they just fouled from fuel?

 

[eyesi]

Ok Nyghtflyer, i double read the entire post again, you said you put delco dist. cap, and i have seen many chevys like your with same symptoms and solution was dist. cap, anyway if it is ok, and timing is okay, then i would check power and grounds at vcm, before try another vcm, really cheap here in america.
Let say something about vcm grounds importance., your VCM have only two pins to eat ground, if only one is lost, partial pcm functions can not be accomplished, pcm drives all actuators (with very very exeptions, and in very very few models) through ground., example, injectors receive 12 v ignition at one wire, the other injector wire comes from VCM carrying pulsating ground, from where? from one or other of the two VCM ground wires so... very very strange things can happen because of bad ground circuits in any electronic control module. So when you hear check the grounds, that is why, not only tighten bolt or nuts, but check reliable ground at harness conector end.