My brother just bought a 4.3l S-10, and kinda got screwed over. Thruck runs fine at slow speeds (his unthorough test drive) but at anything over 40-45, runs with no power, misfires badly, and because of the lack of power application, the transmission doesn't know what to do. I want to troubleshoot the lack of power first before I try to figure out if anything else is wrong.
It idles smoothly, but once in a blue moon stalls out from a start. It has the ABS light and the E brake light permanently in (pretty sure these wouldn't affect motor performance) and no check engine light (Jumpered ports A+B just to make sure).
The motor has the multiport injection.

Similar problem: http://www.truckforum.org/forums/gmc...4-3l-runs.html

I've done some preliminary investigation into the motor bay and found the following from what seems to be an attempt to correct the problem...
-one of the components on the throttle body seems to be a junk yard replacement (yellow paint pen) and the three wires going into it were spliced (not sure if they were put together in the correct order, so I'd like someone to back me up. order of the orginal color wire left to right is brownishgreen, light green, purple) See below picture
-Seems to have all new spark plug wires
-Ignition coil looks pretty new
-There is a zip tie going from the top of the distributor cap down. Not sure if it is holding the cap down, or if there is something else underneath it is holding up

I wanted to start by checking the plug gaps and condition, pulling the distributor cap, and checking the fuel pressure since it seems to be a common problem (which i need to look up how to)

If you have any insight as to how I can best focus my troubleshooting efforts, I would be very grateful. I work alot of crazy hours for the navy.

http://i306.photobucket.com/albums/n...424_061707.jpg
http://i306.photobucket.com/albums/n...424_061654.jpg
http://i306.photobucket.com/albums/n...424_061556.jpg

 

what year is the truck? Is it CPI or TBI? You need to figure out what the point of that zip tie is. I'm thinking its holding down the cap, there isnt much underneath the cap. You need a timing light to shoot timing because it sounds as if it may have been messed with like all other ignition components have been. Test fuel pressure for sure.

 

It's the CPI. (code W in the 8th digit in the vin).

 

And if the zip tie is holding down the cap, could that mean the hold down bolts for the cap might be broke? I'm working midshift this week so I'll get to looking at it in a few days.
I've never done the Fuel pressure test, but from my understanding (and reading), I just have to buy a test gage and hook it up somewhere in the fuel rail? I've found a couple different recommendations for what Fuel pressure should read, but nothing definitive yet. Thanks for the quick respond.

 

yeah, sounds like someone messed up something to hold the cap onto the distributor. that is probably part of your problem.
as far as the fuel test,
there is a port that is like a shcrader valve near the back of the motor that goes into the throttle body. that is where you would hook up the fuel gauge. if i remember what Capt' Hook always says, it should be between 60-66 with the fuel pump running and not drop below 55 for 10 mins. after the pump shuts off. but it might be between 60 and 62.
hook up the gauge and turn the key to the run position, dont start the car. thats where the testing takes place.

 

Hooked up the fuel gage this morning, and it dropped to zero almost immediately

Part 1 -'Spider' Fuel Injector Misfire and Hydrolock (Troubleshooting Case Study)

I pulled off the inlet plenum and keep cycling the fuel pump to check for leaks as the article suggested on page three. I didn't find any, and I think it's have to be significant to have pressure drop as fast as it did when the fuel pump turned off. I think (but don't know) that it might be the fuel pressure regulator bleeding off pressure internally, but not leaking externally. It might also be safer to just replace the whole spider (which looks to come with a fuel pressure regulator in this link... ) to be safe.

Also, one of the injectors wasn't seated in the hole it's supposed to be in. I also didn't see any o rings on the injectors themselves, but the brand new one didn't seem to have them either. Plug gap was good on the one plug I did pull. The distributor cap had a missing tiny screw (hence the zip ties) and the rotor and cap seemed to have alot of buildup on the center nodule. See pictures below.

I think to correct path is to replace the spider (with FPR), rotor, and cap and then see if it runs correctly. Please let me know if I'm on the right path, or if there is a better way to accomplish fixing this problem. Pictures in links below.

http://i306.photobucket.com/albums/n...425_105020.jpg
http://i306.photobucket.com/albums/n...425_105618.jpg
http://i306.photobucket.com/albums/n...425_105629.jpg
http://i306.photobucket.com/albums/n...425_105658.jpg

 

Looks like a regulator leak. The Injectors your referring to are poppet valves, no o-rings there. The injector is in the plastic housing. Your rotor button is also trashed. The map sensor looks like someone replaced the connector, hince the splices. It should be ok as long as the slices are correct. You should get the fuel pressure up to 62 and hold above 50-55 after the spider is replaced. Your on the right track.

 

not experienced with fuel pressure, (though i've read 55+ psi for 10 mins. not much higher than low 60's) but i replaced the spider injector when i got my t10 blazer.

that was all she wrote. runs perfectly now.

i would say you're on the right track. i'm curious to see if my spider has a regulator on it. that would be nice. i have my doubts however.

good luck. you've won 90 percent of the battle by beginning it.

you'll knock it out in no time.

 

yup, that's the one i got... basically anyways. (no o rings on the 6 injector nozzles) but there def should be on the 2 fuel intake main hoses connecting into it.

i paid 80 dollars more than that price too.

make sure you have the right model is all.
napa auto parts had mine that was listed for the 95, but it was a perfect match for my 94.

 

Changed out the injectors, the fuel lines to the injectors, plugs, wires, distributor cap, rotor. Fuel pressure still drops off like before, but not as fast, and the truck still misfires when running down the road. It ran strong at first, then the misfiring kicked in, and it even stalled out once.

Could it be the fuel pump due to the pressure dropping off still, or maybe timing. Kinda at a loss right now. Thanks for the help.