Yet another truck with the infamous light throttle miss when the engine is warm. 150K on truck and no trouble codes. I'm sure there's more work I've done and I'll add that as I remember. Sorry about the unorganized parts rundown; I just tried to think back to what I did on certain weekends.

List of work and observations over last couple months:

1) New 02 sensor; old wiring was cooked. New starter/starter cable.
Added ground strap from block to crossmember. Verified all other
grounds and power wires are in good shape including ECU.
2) Replaced all vacuum lines, "free flowing" cat, Dynomax catback
3) Accel ignition module, coil, cap/rotor (tan). New pickup coil
4) Delco platinum plugs and fresh plug/coil wires 100% covered in
insulator and routed exactly as the factory put them
5) Fuel filter and plenty of system cleaner: Amsoil, Techron, Seafoam
6) Cleaned EGR, upper intake, TB, etc
7) Pulled/cleaned lower intake. Replaced gaskets and properly relsealed
8) Thermostadt and gasket
8.5) Passenger motor mount. All 4 KYB Monomax shocks (awesome)
9) Fuel pressure checks(ed) out as follows with no leak/down:
Priming pump: 62psi
Primed pump: 56psi
Cranking: 66psi
Running (ran, haha): 52-62 (about) and varies accordingly with TP/vacuum,
and does not flutter while driving or missing
10) No apparent leaks inside manifold, but #4 plug was fouled. I'm
assuming the poppet was sticking, or a yet unforseen situation was
causing fuel to fall down the respective drain hole in the lower intake.
So, I got the idea to pull apart the spider myself. Still no apparent
leaks, all o-rings (including FPR) and filters (2) appeared to be
funtioning correctly. Reassembly went great and I tested the poppets
for function with brake cleaner and air pressure. Put everything
together with a new pigtail for the injector. The injector is audibly
making the same noise it used to, and I adjusted the regulator screw
to make the psi match what it was before I took it apart.
11) My issue now is that no fuel will come out of the poppets even while
cranking. I assume that I didn't get the screw in the middle of the
MAXI valve adjusted properly, but can't decide what it's function
even is or what effect it has. If I pour fuel in the intake the truck will run for
few seconds and die.

I hope that makes sense; anyone have experience with this?

Thanks for looking.

 

So, nobody has tried to take one of these apart themselves?
It's a pretty interesting little piece; maybe I'll do a write up after I get it conquered.

 

I had the same issue the last few days where I took the truck a long distance got back and it was cutting out while accelerating I Checked Fuel pressure too, and it was stable at 56PSI the whole time( the CPI needs a minimum of 43PSI to operate, so we're safe there). But it started cutting out worse tonight and so I just kept driving it and it got way worse then died and wouldn't restart. I unplugged the CPI Connector Plug(2 wire plug colors usually red and blue) at the top right of the engine by the MAP sensor. I tested for OHMS and had an Open circuit. So I pulled the Intake Manifold tuning valve and wiggled the plug around and tested again and now I had some resistance. So the plug I bought a year and a half ago from napa was a bad idea when I replaced the CPI. lol. Which is how I ended up here looking for a new plug from GM. Hope this helps. otherwise tell me what else is going on and I'll try to help. Thanks, Sean

 

I finally got it to start, and it made its first decent road trip this weekend. Got excellent mileage relative to what it used to, but if I load it with weight or run the ac it still hesitatates and hunts for gears/lockup depending upon cruising mph.

The error I had made was screwing the MAXI valve adjuster down too far which apparently lets no fuel to the poppets at all even though it flows through the FPR and return line. I had to beat on it to get whatever internal piece I had depressed too far loose again. Playing with that adjustment makes huge differences, but it's still not 100%. I also tried another coil, a reman. ECU, and running with the tuning valve disconnected. As far as I can tell the new CPI harness is working properly even though I have taken it off a hundred times now. I tested that circuit as good as I could without a powered DVOM, and all was good, but I couldn't get specific resistances of course. If there is a way to do that with a regular volt meter let me know; my electronics testing experience is limited.

Thanks for the reply.

 

I was gonna chime in that your adjusting of the screw would be an issue as they are factory set!! looks like u figured that out

 

Yep. I messed it up somehow, and it created an intermittent problem. Gonna steal one from a junkyard I suppose. When I have the spider apart I'll take lots of pictures to show everyone who's curious how it works.