GTBjay

I have a '95 K1500 with a 350 that only sparks when it wants to.
every thing to do with ignition is new, ie, cap, roter, coil, distributor, plugs and wires. what is happing is from time to time it falls flat on it's face with no spark from a stop light or at cruising speeds and putting my foot into it, I have to put it to the floor and within a few seconds it will start to spark, shoot out a bunch of black smoke run only on a few cylinders then slowly get back to running smooth. the truck dose not run like this all the time, but has been getting worse and is still doing it after replacing everything I can think of. I have noticed with the timing light that the timing retards about 10* when this happens in the driveway, and as it slowly starts running again the timing slowly starts climbing back to were it should be.
also it looks like I'm getting weak spark at idol that gets stronger as the rpm rises.

any and all help troubleshooting this will definitely help with my mental stability thank you all in advance

manic

Is it throwing any codes, "check engine light on"
What type of fuel injection throttle body or injectors.

GTBjay

no light, and I rang it out with it throwing no codes at all at me, and it's a TBI, sorry about that, that should of been in the main post.

manic

Might be a clogged fuel filter, or I hate to say fuel pump. Park it in
a dark place, no light, fire it up and see if you see any sparks flying
anywhere, new plugs and plug wires or not there could be a problem.
Look closely around the plugs, might have to rev it up, or even put
in drive to see a actual arc,,worked for me in the past...not throwing
a code, is a teller, but your also poking and hoping...

GTBjay

I don't think it has to do with fuel, I don't have an inline gage on it but I hear the pump doing what it's suppose to do and I'm getting a perfect fan out of the injectors.

and I haven't felt any arking, I ran my fingers over all the wires top to bottom with nothing, and I'm testing the weak spark at the coil.
I'm thinking it must be some random sensor the way it comes and goes, or a chafed wire that I can't find.
what sensor could cause something like this?

manic

If it was a sensor it would throw a code. With a fuel pump you cant
tell by listening to it, although if you dont hear it ticking that is a sign
of failure. Might be a bad coil out of the box, it gets hot and fails..Might
be a intake or vacumm leak,, hard to say. Its not throwing a code so
you have to look at things that the computer doesnt monitor. You say
that when it stumbles and you put your foot down on the gas it takes
off but leaves a puff of black smoke. Tells me the gas is pumping, maybe
to much, maybe not, but the gas isnt burning. So that takes you back
down to fire...

majorahole

im not familiar with that vehicle, so what type sesnor does it use to measure incoming air?
map, maf?
i would believe one of those is your culprit, or at least should get you toward what the problem is